Additional Targets of Fluoroquinolone Antibiotics: Examples and Research (Part 1)

This page is very long.  However, probably about half of the length is due to the reference abstracts I posted directly on this page.  This page is a working draft in progress.  It’s long enough that I’ll probably split it up into another “book” on the website someday. (Actually, it got so long I had to split it into two pages.  This is Part 1, and Part 2 follows this page).    In the meantime,  this page (Part 1) and the next (Part 2) consists of the following topics.  You can scroll down to your topic of interest, or use the “Find Tool” to scan the page for matching words or phrases you’re looking for (on my Windows laptop, the command is to press “Control +F”, which brings up the “Find” box).  Click “Next” at the bottom right of this page to get to Part 2, or use the Menu.  Part 1 ends at “Dysglycemias” and Part 2 starts with “CYP1A2”.

  • Definitions and About the References
  • When it Comes to the Fluoroquinolones, “Wonder Drug” is Just Another Euphemism for “Dirty Drug”
  • You Think You’re Taking a Simple Antibiotic?  Think Again
  • Fluoroquinolones as Cancer Drugs
  • Topoisomerases:   Target for Cancer / Adverse Effects
  • The “Overdose Hypothesis”:   Supra-therapeutic or Increasing Concentrations of FQs Increase the Probability of FQ-Interaction With Human Proteins:   Using Topoisomerase as an Example
  • Tdp1:   Target for Cancer / Adverse Effects
  • MicroRNA:  Target for Cancer / Adverse Effects
  • HIF1a:   Target for Cancer / Adverse Effects
  • Dioxygenases:   P4H, LH1, PHD, JMHD, TET1:   Unintentional Targets / Adverse Effects
  • V-ATPase:   Target for Osteoporosis /Adverse Effects
  • Mitochondria:   Unintentional Target / Adverse Effects
  • NMDA/GABA:   Unintentional Targets / Adverse Effects
  • Dysglycemias / Diabetes:   (HERG, K-ATP, GLP-1, GLUT1, and more):   Unintentional Targets / Adverse Effects  
  • CYP1A2/3A4:   Unintentional Targets / Adverse Effects
  • Flowchart:  CYP1A2 Suppression, and, Living in a Windows 10 World While Running on Windows 3.1 
  • Phosphodiesterases:   Target for Studies / Unintentional Targets / Adverse Effects
  • Immunomodulatory / Kinase Inhibitors:  Target for Studies / Unintentional Targets / Adverse Effects
  • Cytotoxicity and Oxidative Stress Related:   Unintentional Targets / Adverse Effects
  • Cardiac:   Unintentional Target / Adverse Effects
  • Aldehyde Dehydrogenases:   Unintentional Target / Adverse Effects
  • Viral DNA/RNA and proteins:   Target for Anti-viral / Adverse Effects
  • Fungal DNA and proteins:   Target for Anti-fungal / Adverse Effects
  • Plant DNA:   Target for Herbicide / Adverse Effects
  • Environmental pollution:   Resistance / Adverse Effects


The next time a doc wants to give you an FQ, print out the “FQ’s for Cancer” references (scroll down this page) and ask if you really need a chemo drug for your infection.    Also ask if they think there might be a concern that so many other types of pretty important proteins in the body are negatively affected by FQ’s too, and if those could be the cause or contributing to some of the severe “side effects” that have been reported (scroll down further for more references).   Then ask them if they’re aware that plenty of their colleagues have been felled by these “antibiotics” as well, see  FQ Adverse Effects In Their Own Words from Physicians .   Ask them to review Recommendations for the Responsible Use of Fluoroquinolone Antibiotics.    And then ask them again:  Do I REALLY NEED this FQ antibiotic for my infection?

The interest in regulating or solving the problem of FQ ADR’s was never high to begin with, but I think it has decreased substantially even more recently.   So it will be “buyer beware” (or, “patient beware”) more than ever now (see How to (Try) to Protect Yourself from ADR’s:  The Six Big Clues I Wish I Had Seen).  Meaning:  “YOYO” (You’re On Your Own) when it comes to knowledge and safety about these drugs.

This page is long and somewhat technical (although much of the length and technicality is due to the references I am providing directly on the page).   For those of you who don’t understand much of what’s written on this page, just remember: “If it ends in ‘-oxacin’, it’s a toxin”.

For those of you attempting to research and elucidate potential mechanisms involved in FQT/FQAD, there is a nice mix of references, organized by “FQ targets” on this page that will help. These are by no means all the references available on these topics.  I simply pulled “a few” of them out from the thousands that are available on the internet.  But they should help to get you started in your search.  They also, along with the rest of this website, provide some clues as to where the problems may lie in those of us with FQT/FQAD.

I throw out a lot of ideas here.   As always, my observations and experiences of my own reaction are valid; my interpretations of them in terms of potential mechanisms are always open to question.  In my opinion, it will take millions and millions of dollars and some dedicated research by a multitude of specialties before we get any real answers to the problem of FQT/FQAD.   Until or unless that happens, we victims are on our own to record our own experiences and interpret them the best we’re able, while we wait for the FDA, Pharma, the medical professionals, and the research scientists to do their part.


Definitions and About the References

Drug Promiscuity”:   Drug Promiscuity is defined as the property of a drug to act with multiple molecular targets and exhibit distinct pharmacological effects.  Promiscuous drugs are the basis of polypharmacology and the causes for side effects.  When undesired, promiscuity is a major safety concern that needs to be detected as early as possible in the drug discovery process.   (1, 2, 3 )

Dirty Drugs”:  (From Wiki):    In pharmacology, a dirty drug is an informal term for drugs that may bind to many different molecular targets or receptors in the body, and so tend to have a wide range of effects and possibly adverse drug reactions.

Additional Targets”:  All of the other enzymes, transporters, receptors, and other proteins in the human body that the FQ’s interact with or affect in addition to their intended “main target” of the bacterial enzyme called “topoisomerases”.

List of Additional TargetsI cover on this page:  FQ’s interact with and affect numerous human molecular targets, and are not specific to targeting only bacteria.  The number and variety of these “targets” can be seen by reviewing the research abstracts I provide on this page.

References:  FQ’s are a hot topic for drug development overall, and this is shown by the description of many thousands of derivatives in the literature.   For this page, I  pulled up examples based on known FQ targets.   As you scroll or read through these abstracts, keep in mind several things:

  • Most studies on the development and efficacy, as well as potential genotoxicity and cytotoxicity of FQ’s are funded by Pharma.   Therefore, expect a lot of careful wording, minimizing the dangers of these drugs, while maximizing the efficacy and safety of them.   Remember, “Wonder Drugs” translates to “Wonder Profits”, which is what drives “Publishing Bias” ( 1, 2, 3, 4 ) all around.
  • Because of what’s happened to me and tens or hundreds of thousands of others with FQT/FQAD, I am biased in the other direction – towards safety as well as efficacy.   This is particularly true when it comes to these drugs acting as chemotherapy agents and topoisomerase inhibitors.    Pharma minimizes the fact that these drugs kill normal (non-cancerous) cells in addition to cancer cells, or that these drugs target human topoisomerase enzymes as well as the bacterial topoisomerase enzymes.   So you will find plenty of that if you read through the literature.    I, on the other hand, focused on and highlighted parts of the abstract the clued us in to, or directly stated, otherwise, and this is my bias for the references I provide on this page.
  • An important point to consider is that the toxicity of quinolones and fluoroquinolones is a class effect.   It doesn’t matter which drug within this class we’re talking about; it doesn’t matter if it functions as an antibiotic, anti-neoplastic , anti-viral, or anti-fungal agent, it doesn’t matter what molecular structures are added or removed from the basic quinolone pharmacore, and it doesn’t matter which brand name FQ antibiotic (Cipro, Levaquin, Avelox, etc) that you take:    The basic quinolone and fluoroquinolone scaffold has the potential to cause FQT/FQAD, as evidenced by the long history of these adverse reactions, going back to nalidixic acid.   The many thousands of variations, or “derivatives” of the basic quinolone nucleus, will indeed shift the drug more or less to different biological targets, or increase or decrease the toxicity of these drugs to human cells to whatever extent.   But history has shown us it doesn’t matter how you dress up the basic building block structure of this drug:    it’s toxic to a certain number of people in the population.    It’s the quinolone structure that seems to not only allow it to function so promiscuously, but makes it so potentially toxic too.    And that’s a problem.
  • Because of the above point I just made, don’t be fooled when reading the research about the “safety” of these drugs.   Those of us with FQT/FQAD took probably the “safest version” of these drugs – the “simple antibiotic” – in the lower “antibiotic doses” — and look what happened.    And until it’s known why that happened, and who in the population are at risk, these drugs are not safe at any dose.

Here is an example of the kinds of reassurances presented within most publications regarding the safety of FQs:

Drugging Topoisomerases: Lessons and Challenges       “Topoisomerase inhibitors are exquisitely selective and without ambiguity eligible as “targeted therapies”. Clinically relevant Top1 inhibitors do not affect Top2, and, conversely, Top2 inhibitors do not trap Top1 enzymes. Furthermore, the inhibitors of bacterial topoisomerases (gyrase and Topo IV) are inactive against host cell topoisomerases (Top2 and Top1), which accounts for their antibacterial potency without impact on the host genome. . . . Prokaryotic Top2s are excellent targets because: 1) they are essential in all bacteria; 2) cleavage complexes are bactericidal (not just bacteriostatic); 3) their targeting does not affect host human enzymes (their selectivity is at least three order of magnitude higher for prokaryotic over eukaryotic enzymes); 4) the high degree of homology between gyrase and Topo IV5 enables the targeting of both enzymes and therefore the killing of a broad spectrum of bacteria with a single drug.”

This all sounds very reassuring.   And the facts are, many people appear to take these antibiotics successfully and without injury, at least, that they know of yet.   But in practice, these delineations are not a rock solid given, as evidenced by the growing number of people recognized to have FQT/FQAD.   They’re also not a rock solid given in the research lab either, if you carefully read through the many publications.

Here’s a different take that should be worrisome:

G-Quadruplex Structures in the Human Genome as Novel Therapeutic Targets.   “It is now emerging that G-quadruplex structures may act as key regulators of several biological processes. Consequently, they are considered as attractive targets for broad-spectrum anticancer therapies, and much effort is being made to develop a variety of ligands with improved G-quadruplex recognition properties.   Quarfloxin (CX-3543), a fluoroquinolone derivative designed to target a G-quadruplex within ribosomal DNA and disrupt protein-DNA interactions, has entered clinical trials for different malignancies” . . . These compounds (Figure 2), belonging to a variety of chemical classes (e.g., cationic porphyrins, antraquinones, perylenes, fluoroquinolones (norfloxacin, ciprofloxacin), piperazines, pentacyclinacridinium salts, fluoroquinophenoxazines, ethidium derivatives, isoquinoline and benzylisoquinoline alkaloids, naphthalene diimides, bisquinolinium compounds, carbazole derivatives), share common features, such as the presence of a flat aromatic surface, of cationic charges as well as the ability to stack on or intercalate in targeted G4 structure.

For anyone who has been floxed for a while and researching this, some of these compounds should look familiar:   the quinolines, as well as the quinolones, quinones, cationic porphyrins, piperazines, alkaloids . . . . the commonalities of these are what we might be sensitive to and what we need to be looking for.   For everyone else, the fact that these compounds and their derivatives are used in other common drugs, and are targeting DNA structures,  should be a little concerning, to say the least.

Again, yes, it is true that minute differences in FQ molecular structure can shift the drug more or less to different biological targets, or increase or decrease the toxicity of these drugs to human cells to various extents.   But keep in mind, that if minute differences in FQ molecular structure can make such a difference between drug-protein interactions, then minute differences in our DNA/protein structure could equally do the same.  FQ toxicity is a class effect.   People have been hurt by these drugs since they were first synthesized, and it bears repeating:  History has shown us it doesn’t matter how you dress up the basic building block structure of this drug:    it’s toxic to a certain number of people in the population.    It’s the quinolone structure that seems to not only allow it to function so promiscuously, but makes it so potentially toxic too.    And that’s a problem.


When it Comes to the Fluoroquinolones, “Wonder Drug” is Just Another Euphemism for “Dirty Drug”

Fluoroquinolones, and the quinolones, are too often hailed as “Wonder Drugs” because they “get everything”.   They not only function as antibacterials, but as anti-viral, anti-fungal, anti-inflammatory, and most importantly and potentially sinister of all, as anti-neoplastic (anti-cancer or chemotherapeutic) agents.   Of course, what this really translates to, as much or more than any of the “Wonder Health Benefits” these drugs may provide, are the “Wonder Profits” they will bring in for Pharma.   Dirty Money from Dirty Drugs is nothing new.   The people at the top of these “Drug Cartels” – whether illegal ones, or the legal ones in the form of Pharma/FDA – don’t care how many lives are lost or damaged in the process.   Which is why these drugs will continue to be pushed onto an unsuspecting public en masse as aggressively as possible for as long as possible, until the unsustainable burden of severe and disabling chronic illnesses collapses the entire system.

It is obvious that the quinolone pharmacore, and the fluoroquinolone drugs, can be useful drugs used in appropriate situations (see Responsible Use of Fluoroquinolone Antibiotics).    But the promiscuity of these drugs also make them one of the most, if not the most, insidiously dangerous dirty drugs legally given en masse to an unsuspecting public on the market today.


You Think You’re Taking a Simple Antibiotic?  Think Again

Here, on this webpage, I go through just a few of those “additional targets” that are affected and potentially damaged in your body when you take these “simple antibiotics”.    Keep in mind that FQT/FQAD is a class effect of these drugs.   This means that ALL fluoroquinolone and quinolone drugs, as a class, have the potential to cause severe, disabling, catastrophic, devastating, long term and permanent harm.   This means it doesn’t matter which FQ you take — you are at risk.  As to who will be affected, and when, is probably a function of underlying genetic and epigenetic variations which will determine for how long and how effectively your body and cells can offset and repair the damage that is caused.   Since none of this is known yet, this means everyone is at risk every time they take the drug.   A body can only handle so much toxic insult before succumbing, so it may indeed, be just a matter of time for everyone.

FQ’s target and damage underlying, fundamental, ancient, and conserved molecular structures common to all life including bacteria, viruses, fungi, plants, and humans.   Many of the enzymes that FQ’s target are involved in DNA replication and repair – absolutely necessary to keep life – and you – alive and functioning.   Without proper DNA replication and repair, you will die, sooner or later.    And as anyone with permanent FQT/FQAD can attest, it can be a long, slow, agonizing, miserable decline full of suffering.    So you might want to think again before putting this known toxic poison “Wonder Drug” into your body to treat your simple uncomplicated infection, or an infection you don’t even have yet prophylactically for “just in case”.

With the fluoroquinolone antibiotics, we have a drug that knowingly targets multiple DNA replication and repair enzymes and DNA directly, as well as creates epigenetic modifications on DNA.    They are also very well known chelating agents, and are also promiscuously binding to, inhibiting, or interacting with any number of additional known and unknown molecular structures in your body.  The list of just how much these drugs interact with and affect our own human proteins and cells continues to grow.   They are not simply “targeting the bacteria” as advertisers in the pharmaceutical industry and the medical profession would lead you to believe.   They are not just “simple antibiotics”.    Behind the scenes, there are thousands of studies, being done on tens of thousands of quinolone derivatives, to further promote their use as cancer drugs, and for treatments of viral and fungal infections, and even as herbicidal agents.   Pharma is more than willing to spend millions to develop this class of drugs for their anti-cancer, anti-viral, anti-fungal, anti-bacterial, and herbicidal potential due to their promiscuous nature.   The flip side, of course, is that they’re very unwilling to acknowledge that it’s this very same promiscuity of this “anti-life” class of drugs that make them so potentially dangerous to humans and mammals as well.

For all the non-science people reading this, you don’t have to know, understand, or remember the details of the various target proteins with their strange names and symbols.   All you really have to understand is that these are some pretty heavy duty proteins that are absolutely necessary for life and for any quality of life for us.   And that by damaging or destroying these enzymes, FQ’s are destroying us – and life.   This is not simply being dramatic.   If FQ’s only targeted bacteria, the way that they are advertised, none of us would have FQT/FQAD and there wouldn’t be a problem.  But they’re not targeting only bacteria.  They are targeting numerous enzymes, transporters, receptors, and DNA of humans too.   And in the effort to develop these drugs into anti-cancer, anti-viral, anti-fungal, anti-bacterial, and herbicidal agents, there is plenty of available research that documents this.


Fluoroquinolones as Cancer Drugs

One of the things you might notice as you go through the list, is how often the FQ’s are suggested for use as anti-neoplastic and anti-tumor drugs.   This is because they are, in fact, anti-cancer chemotherapeutic drugs.   Cancer, by definition, is “unregulated growth”.   Cancer cells need extra nutrients, oxygen and an extra blood supply to grow faster than “normal” cells, and to spread.   Therefore, anything that slows down, inhibits, or stops cell growth, survival, proliferation, and migration, or prevents cells from using up resources such as glucose, oxygen, or blood supply, can function as a cancer drug (ie, an anti-neoplastic agent).

It turns out that FQ’s are great at doing all the above.  Their mechanisms of causing cell death range from direct DNA breakage and damage, to cutting off nutrients and blood supplies for those nutrients.   This might explain why some of us with FQT/FQAD lose our hair and nails, are chronically nauseated and lose 20-50 pounds, have severely dry eyes, mouth, and skin, strange skin rashes, lose the ability to sweat, have permanent peripheral neuropathy, muscle aches, headaches, fatigue, endocrine and neuroendocrine symptoms, and “chemo brain”/ “brain fog” CNS symptoms during the acute stage or as delayed symptoms.    This is in addition to the well known but peculiar FQ-Induced adverse affect of targeting collagens, resulting in documented tendon pain and ruptures, detached retinas, and aortic aneurysms

With the exception of the tendon issues, note how many of the above symptoms are similar to what patients with cancer go through during chemotherapy treatment.  Except, in those of us with FQT/FQAD, the symptoms are permanent.   Indeed, I’ve often described my experience like “going through a brutal round of chemotherapy every day of my life”.

If you have cancer, you might want to consider taking an FQ for it.   In a last ditch effort to save your life, you might consider blasting your body with an FQ or other chemo drug at high enough doses to “kill the cancer, but not you”.    If you have a severe life threatening infection, with NO other options available, you might also want to consider taking an FQ.   In lower dosages, for short duration, and hopefully only once in your life, taking an FQ could save your life, hopefully without doing so much damage to your own cells that your body, once healed, can’t repair and recover from it.

For everyone else and the rest of us without cancer:    I wouldn’t recommend taking a chemotherapy drug for your simple infection or suspected infection.   For those of you who have taken the FQ’s safely – or believe you have – I would say there’s a chance you don’t know or feel the consequences yet.   Because of the FQ’s mechanism of action, it can be weeks, months, or years before you finally start feeling the effects of damaged DNA replication and repair enzymes, damaged DNA, and damaged mitochondria.   By the time that happens, you might never suspect that antibiotic you took once – or multiple times – long ago as playing a role in your chronic health problems.    And to Pharma’s benefit, you will have no way to prove it either, even if you do.   Much like cigarettes, Hepatitis C, Lyme’s disease, Syphilis, or chemotherapy for cancer, the carcinogenic and damaging effects of FQ’s can occur long after the original insult, and creep up on you insidiously.   This is because FQ’s target some pretty important enzymes and proteins that bacteria, viruses, fungi, plants, and humans all have in common.

As of this writing, no one knows who, when, how, or why some people are affected more than others, earlier than others, worse than others, have immediate or delayed effects, or appear to come out unscathed after using FQ’s.   There is even the chance that no one comes out unscathed, given enough time, even if we don’t know or understand how that happens yet.    And until that’s known, why take the risk?

Fluoroquinolones are a hot topic being studied for their efficacy in the following types of cancer:   colon cancer, bladder cancer, prostrate cancer, bone cancer, lung cancer, pancreatic cancer, breast cancer, nerve tissue cancer (neuroblastoma), blood cell cancer (leukemia), and squamous cell carcinoma.  There are probably thousands of studies of FQ’s for their anti-cancer properties.  Below are just a few of those published references to get your started.   Print these out for your doctors and pharmacists.

Does ciprofloxacin have an obverse and a reverse?   “Ciprofloxacin is an antibiotic that belongs to fluoroquinoles, characterized by broad spectrum of action against pathogens, especially Gram(-) aerobic bacilli. For a long time, it has been thought that ciprofloxacin has an effect only on bacterial cells. Now it is known, that this drug can significantly affect eukaryotic cells including human cancer cells. Its bactericidal action rely on inhibition of topoisomerase II, enzyme responsible for alterations in 3D structure of DNA during replication, transcription and chromatin condensation. Thanks to that, ciprofloxacin can induce cell cycle arrest and apoptosis of cancer cells. The effectiveness of ciprofloxacin was confirmed in several in vitro studies on tumor cell lines such as: human bladder cells, leukaemic cell lines, human osteosarcoma cells, human prostate cancer cells, human colorectal carcinoma cells and human non-small cell lung cancer cell line. Ciprofloxacin is particularly effective against non-small cell lung cancer mainly due to accumulation of ciprofloxacin in lung tissue after intravenous administration and its toxicity against lung cancer lines in vitro in a concentration and time-dependent manner.”

Ciprofloxacin decreases survival in HT-29 cells via the induction of TGF-beta1 secretion and enhances the anti-proliferative effect of 5-fluorouracil.    “In the present study, we demonstrated that ciprofloxacin inhibits proliferation of the colonic epithelial adenocarcinoma cell line HT-29 in a concentration- and time-dependent manner. These results extend those found previously showing the antiproliferative effect of ciprofloxacin on human cancer cell lines. The antitumour efficacy of ciprofloxacin and other members of the fluoroquinolone family has been reported in several cancer cell types including leukaemic, bladder, prostate, osteoblast, osteosarcoma, neuroblastoma and colon cancer cell lines”.

Role of mitochondria in ciprofloxacin induced apoptosis in bladder cancer cells.   “The disruption of calcium homeostasis, mitochondrial swelling and redistribution of Bax to the mitochondrial membrane are key events in the initiation of apoptotic processes in ciprofloxacin treated bladder cancer cells.”

Ciprofloxacin mediated cell growth inhibition, S/G2-M cell cycle arrest, and apoptosis in a human transitional cell carcinoma of the bladder cell line.   “The results of our current studies provide strong experimental evidence for the use of ciprofloxacin as a potential preventive and/or therapeutic agent for the management of transitional cell carcinoma of the bladder.”

The cytotoxic effect of fleroxacin and ciprofloxacin on transitional cell carcinoma in vitro.    “Fleroxacin and ciprofloxacin significantly affect cell proliferation in transitional cell carcinoma cell lines. The results encourage further study of the possibility of clinical application of some fluoroquinolones to prevent recurrence of urinary bladder tumors because the urinary excretions after oral administration of these drugs are quite high.”

Ciprofloxacin induces apoptosis and inhibits proliferation of human colorectal carcinoma cells.   “Ciprofloxacin decreases proliferation and induces apoptosis of colon carcinoma cells, possibly in part by blocking mitochondrial DNA synthesis. Therefore, qualification of ciprofloxacin as adjunctive agent for colorectal cancer should be evaluated.”

Suppression of human prostate cancer cell growth by ciprofloxacin is associated with cell cycle arrest and apoptosis.   “At doses 50-400 micro g/ml ciprofloxacin, the concentrations that are normally achieved at doses currently used for the treatment of anti-bacterial infections, inhibited bladder cancer cell growth and induced S/G2M arrest with modulation of key cell cycle regulatory genes and ultimately activated apoptotic processes. . . These results suggest the potential usefulness of the fluroquinolone, ciprofloxacin as a chemotherapeutic agent for advanced prostate cancer.”

Repositioning of antibiotic levofloxacin as a mitochondrial biogenesis inhibitor to target breast cancer.   “Targeting mitochondrial biogenesis has become a potential therapeutic strategy in cancer due to their unique metabolic dependencies. In this study, we show that levofloxacin, a FDA-approved antibiotic, is an attractive candidate for breast cancer treatment . . . Importantly, levofloxacin inhibits mitochondrial biogenesis as shown by the decreased level of mitochondrial respiration, membrane potential and ATP. In addition, the anti-proliferative and pro-apoptotic effects of levofloxacin are reversed by acetyl-L-Carnitine (ALCAR, a mitochondrial fuel), confirming that levofloxacin’s action in breast cancer cells is through inhibition of mitochondrial biogenesis. A consequence of mitochondrial biogenesis inhibition by levofloxacin in breast cancer cells is the deactivation of PI3K/Akt/mTOR and MAPK/ERK pathways.”

In vitro effects of ciprofloxacin and pefloxacin on growth of normal human hematopoietic progenitor cells and on leukemic cell lines.   “Ciprofloxacin and pefloxacin caused dose-dependent inhibition of colony formation both from normal bone marrow cells and from the leukemic line K-562 cells. . . . It is concluded that ciprofloxacin does not exert in vitro inhibitory effect on human leukemic cells when assayed at concentrations of less than or equal to 5 micrograms/ml. However, at concentrations of 25 and 50 micrograms/ml of ciprofloxacin alone and in combination with several antineoplastic agents exerts an inhibitory effect on colony formation”

Inhibitory effects of the quinolone antibiotics trovafloxacin, ciprofloxacin, and levofloxacin on osteoblastic cells in vitro.   “Treatment of confluent cultures with trovafloxacin, ciprofloxacin, or levofloxacin resulted in strong inhibition of calcium deposition, as determined on day 14 by alizarin red staining and biochemical analysis. The effect was apparent with 2.5-5 microg/ml of each of the three antibiotics tested and progressively increased to more than a 90% decline in the calcium/protein ratio with 20-40 microg/ml antibiotic concentration.”

Effect of ciprofloxacin on the proliferation of osteoblast-like MG-63 human osteosarcoma cells in vitro.    “Locally applied antibiotic therapy is gaining popularity for the treatment of infections associated with open fractures and posttraumatic osteomyelitis. With use of local techniques, ciprofloxacin levels as high as 1,300 microg/ml, or over 200 times the bone levels achieved with intravenous administration, have been reported. . . .  The results of this study demonstrated that ciprofloxacin caused significant decreases (p < 0.05) in cell number at 40 microg/ml at 24 hours and 20 microg/ml at 72 hours. [3H]thymidine incorporation per cell decreased significantly at levels of 80 microg/ml at 24 hours and 20 microg/ml at 72 hours. The authors conclude that reported local levels of ciprofloxacin seen in vivo inhibit the proliferation of human osteoblast-like cells in vitro.”

Reversal of multidrug resistance-associated protein-mediated drug resistance in cultured human neuroblastoma cells by the quinolone antibiotic difloxacin.   “The data demonstrate that difloxacin can reverse drug resistance in unselected human neuroblastoma cells and is therefore a potential candidate for future clinical trials.”

Synthesis and potential antitumor activity of 7-(4-substituted piperazin-1-yl)-4-oxoquinolines based on ciprofloxacin and norfloxacin scaffolds: in silico studies.   “These compounds exhibit potent and broad spectrum antitumor activities using 60 human cell lines in addition to the inherent antibacterial activity.”

Quinolone antibiotics: a potential adjunct to intravesical chemotherapy for bladder cancer.   “Anticancer drugs such as doxorubicin target topoisomerase II as do the quinolone antibiotics. We evaluated two fluoroquinolones independently and in combination with doxorubicin for cytotoxic effects against bladder cancer cells in vitro . . . Ciprofloxacin and ofloxacin exhibit significant time- and dose-dependent cytotoxicity against transitional carcinoma cells and significantly enhance the cytotoxicity of doxorubicin. These effects occur at concentrations achievable in the urine of patients after oral administration. This suggests that quinolone antibiotics might be useful as an adjunct to intravesical chemotherapy and might reduce seeding of cancer cells after transurethral resection of bladder tumors.”

Inhibition of human transitional cell carcinoma in vitro proliferation by fluoroquinolone antibiotics.   “The in vitro effects of the fluoroquinolone antibiotics ciprofloxacin and ofloxacin upon 3 human transitional cell carcinoma cell lines were investigated at concentrations that are attainable in the urine of patients taking these drugs orally . . . Ciprofloxacin and ofloxacin inhibit proliferation and DNA synthesis of these 3 human TCC lines in vitro. Inhibition occurred in a concentration- and time-dependent manner. The concentrations that were assessed are attainable in the urine of patients taking these agents orally.”

Increased cytotoxicity of squamous cell carcinoma of the head and neck by combining cisplatin with VP-16 and ciprofloxacin.     “Chemotherapeutic treatment of squamous cell carcinoma (SCC) of the head and neck has been largely ineffective because of tumor cell resistance. This study examined combinations of cisplatin, 4′ demethylepipodophyllotoxin ethylidene D-glucoside (VP-16), and ciprofloxacin, a quinolone antibiotic. VP-16 and ciprofloxacin were used in an effort to inhibit DNA repair and increase cytotoxicity. Chemotherapeutic agents often have a direct damaging effect on cellular DNA. Cytotoxicity may be the result of incomplete DNA repair mechanisms; whereas tumor cell resistance to drugs may be due to efficient DNA recovery. A nuclear enzyme especially important to DNA repair and cell growth is topoisomerase II (topo II). Targeted inhibition of topo II by VP-16 and ciprofloxacin may cause increased cisplatin cytotoxicity . . . Four of five SCC lines examined demonstrated significant augmentation of cisplatin cytotoxicity with the addition of both VP-16 and ciprofloxacin. These in vitro data suggest methods may exist for improving the chemotherapeutic treatment of SCC of the head and neck.”

Moxifloxacin and ciprofloxacin induces S-phase arrest and augments apoptotic effects of cisplatin in human pancreatic cancer cells via ERK activation.   “Pancreatic cancer, one of the most dreadful gastrointestinal tract malignancies, with the current chemotherapeutic drugs has posed a major impediment owing to poor prognosis and chemo-resistance thereby suggesting critical need for additional drugs as therapeutics in combating the situation. Fluoroquinolones have shown promising and significant anti-tumor effects on several carcinoma cell lines . . . Herein, we found that both the fluoroquinolones suppressed the proliferation of pancreatic cancer cells.”

Trovafloxacin-induced replication stress sensitizes HepG2 cells to tumor necrosis factor-alpha-induced cytotoxicity mediated by extracellular signal-regulated kinase and ataxia telangiectasia and Rad3-related.   “Use of the fluoroquinolone antibiotic trovafloxacin (TVX) was restricted due to idiosyncratic, drug-induced liver injury (IDILI). Previous studies demonstrated that tumor necrosis factor-alpha (TNF) and TVX interact to cause death of hepatocytes in vitro that was associated with prolonged activation of c-Jun N-terminal kinase (JNK), activation of caspases 9 and 3, and DNA damage . . . The data suggest a complex interaction of TVX and TNF in which TVX causes replication stress, and the downstream effects are exacerbated by TNF, leading to hepatocellular death. These results raise the possibility that IDILI from TVX results from MAPK and ATR activation in hepatocytes initiated by interaction of cytokine signaling with drug-induced replication stress.”

Molecular aspect on the interaction of zinc-ofloxacin complex with deoxyribonucleic acid, proposed model for binding and cytotoxicity evaluation.   “Recently, several studies have shown that the metal-fluoroquinolone complexes have more antibacterial and cytotoxic effects in comparison with free fluoroquinolones. These results may introduce new drugs for chemotherapy with fewer side effects.”

DNA binding, photo-induced DNA cleavage and cytotoxicity studies of lomefloxacin and its transition metal complexes.   “This work was focused on a study of the DNA binding and cleavage properties of lomefloxacin (LMF) and its ternary transition metal complexes with glycine . . . Antimicrobial and antitumor activities of the compounds were also studied against some kinds of bacteria, fungi and human cell lines.”

DNA repair inhibition by UVA photoactivated fluoroquinolones and vemurafenib.   “Cutaneous photosensitization is a common side effect of drug treatment and can be associated with an increased skin cancer risk . . . Despite widely different structures and modes of action, each of these drugs potentiated UVA cytotoxicity. UVA photoactivation of 6-TG, ciprofloxacin and ofloxacin was associated with the generation of singlet oxygen that caused extensive protein oxidation. In particular, these treatments were associated with damage to DNA repair proteins that reduced the efficiency of nucleotide excision repair.”

Ciprofloxacin containing Mannich base and its copper complex induce antitumor activity via different mechanism of action.   “The Mannich base containing ciprofloxacin and kojic acid structural units was prepared and evaluated in antitumor activity . . . The cytotoxicity of the Mannich base was involved in apoptosis, cell cycle arrest, depolarization of mitochondrial membrane and weaker topoisomerase II inhibition, but the copper complex exerted its cytotoxicity mainly through dual topoisomerase inhibition, especially stabilizing the intermediate of cleavage DNA-topoisomerase complex.”

Cu(Nor)2·5H2O, a complex of Cu(II) with Norfloxacin: theoretic approach and biological studies. Cytotoxicity and genotoxicity in cell cultures.   “Norfloxacin is a fluoroquinolone antibiotic used in the treatment of bacterial infections. In this article, we studied the potential antitumoral action of a complex of Norfloxacin with Cu(II), Cu(Nor)(2)·5H(2)O on osteosarcoma cells (UMR106) and calvaria-derived cells (MC3T3-E1), evaluating its cytotoxicity and genotoxicity . . . Altogether, these results suggest that Cu(Nor)(2)·5H(2)O is a good candidate to be further evaluated for alternative therapeutics in cancer treatment.”

Ciprofloxacin and epirubicin synergistically induce apoptosis in human urothelial cancer cell lines.     “This study provides evidence that ciprofloxacin and epirubicin exhibit synergistic cytotoxic effects in vitro.”

HERG K+ channel related chemosensitivity to sparfloxacin in colon cancer cells.     “Potassium channels are essential for the regulation of cell proliferation. As reported, HERG protein is overexpressed in a wide range of human tumors, including colon carcinoma. The aim of this study was to investigate the effects of antibacterial agents sparfloxacin (SPFX), a blocker of HERG channel, on HERG K+ channel highly expressing colon cancer cells . . . The cell viability of the colon cancer cells was inhibited by SPFX in a dose-dependent manner. SPFX induced apoptosis and inhibited migration and invasion of colon cancer HCT116 cells. The increase in apoptosis was associated with a decrease in procaspase-3 and Bcl-2 protein expression. Study with herg-transfected HEK293 cells and siRNA-knock down HCT116 cells confirmed that the cell viability inhibition by SPFX was correlated with HERG expression . . . Our finding suggested that SPFX could be a biochemical modulator in treatment of colon cancer with chemotherapeutic drugs.”

Synthesis and antitumor activity of C3 heterocyclic-substituted fluoroquinolone derivatives (I): ciprofloxacin aminothiodiazole Schiff-bases.   “To discover a novel antitumor lead compound derived from fluoroquinolone, C3 carboxyl group of ciprofloxacin (1) was replaced with heterocyclic ring to form cyclopropyl fluoroquinolone aminothiadiazole scaffold (2), then reacted with aromatic aldehydes to give the Schiff bases compounds (3a-3j) . . . Therefore, the C3 carboxyl group of fluoroquinolone is not necessary to antitumor activity. Functionally modified heterocycle-substituted fluoroquinolone as potent antitumor lead compound is valuable for further study.”

Inhibition of cell growth and induction of apoptosis in human prostate cancer cell lines by 6-aminoquinolone WM13.   “Fluoroquinolones affect the proliferation and apoptotic cell death of several human malignancies. Therefore, we investigated whether new 6-aminoquinolone derivatives, initially synthesized as anti-HIV agents, could affect the proliferation and apoptotic cell death of human prostate cancer cell lines . . . Cytotoxicity, which was more pronounced in LNCaP, was accompanied by morphological changes, DNA damage, arrest at the S/G(2)/M phase of the cell cycle, and an increase of the sub-G(1) population. Molecular mechanism underlying WM13-induced cell death involved caspase-8 and -3 and modulation of the expression of apoptotic genes, as well as cleavage of poly-ADP ribose polymerase.”

G-Quadruplex Structures in the Human Genome as Novel Therapeutic Targets.   “It is now emerging that G-quadruplex structures may act as key regulators of several biological processes.  Consequently, they are considered as attractive targets for broad-spectrum anticancer therapies, and much effort is being made to develop a variety of ligands with improved G-quadruplex recognition properties.   Quarfloxin (CX-3543), a fluoroquinolone derivative designed to target a G-quadruplex within ribosomal DNA and disrupt protein-DNA interactions, has entered clinical trials for different malignancies”


Topoisomerases:  Targets for Cancer

In the section above, I described and provided evidence that FQ’s are chemotherapy drugs.   Here, I provide information on the first of many mechanisms as to why that is:    the topoisomerase enzymes as a target for cancer.

Topoisomerases are enzymes absolutely necessary for DNA and cell replication. The FQ’s target bacterial topoisomerases, stopping DNA replication, which is what kills the bacteria. When FQ’s target topoisomerase enzymes, they stop these enzymes from working by creating permanent DNA breaks in the bacteria. With permanent DNA breaks, the bacteria cannot replicate or reproduce, and so are killed.

Human topoisomerase enzymes are also the target of many cancer drugs, including FQ’s. These cancer drugs target fast growing cancer cells, stopping DNA replication, which is what kills the cancer cells. Whether killing bacteria, or killing cancer cells, the mechanism of these topoisomerase poisons, which consist of many different types of chemotherapy drugs and FQ’s, is pretty much the same.   Breaking the DNA stops replication –leading to death, for cancer and for bacteria.

Why are FQ’s and other topoisomerase-based chemotherapy drugs such effective anti-cancer agents? It’s the rate of cell growth that often defines the difference between what cells a cancer drug will target. Since topoisomerases are absolutely needed for replication, the faster cells replicate, the more topoisomerase enzymes are used. This is why “topoisomerase inhibitors” and “topoisomerase poisons”, can be such effective cancer treatments. The unregulated and faster growth of cancer cells makes them a prime target. Most people understand this concept in the form of chemotherapy drugs trying to “kill the cancer without killing you”, ie, kill faster growing cancer cells without killing cells growing at a normal rate.   However, there are plenty of normal cells in the body that need to be continually replaced and tend to replicate faster than others. Normal cells that grow fast tend to be hit by chemo too, producing the classic side effects of many chemotherapies: hair loss, nausea, dry eyes, mouth and skin, diarrhea, fatigue, low blood count, and compromised immune system.   For the non-science people reading this, some nice explanations of this concept can be found in this Quora discussion here:     Why Does Chemotherapy Only Affect Fast Growing Cells?     “Chemo brain”, another classic side effect of chemotherapy, may not occur directly by topoisomerases as most neurons within the brain typically don’t replicate. However, they are most likely being affected secondarily, or via other mechanisms. Additionally, when “Labile Cells” are being affected, the risks of mutations within the stem cells themselves increase. This could account for the long term, permanent, or delayed “chemo” effects of FQ’s, depending on the mutations involved, how viable the cells are, and whether enough of a healthy cell population exists such that recovery is possible.

There are several different types of topoisomerase enzymes. Bacterial topoisomerase enzymes are slightly different from human topoisomerase enzymes. In theory, and on paper, it’s these slight differences that determine whether or not an FQ will target the bacterial topoisomerases, or human topoisomerases. In addition, slight changes in the molecular structure of FQ’s themselves help to determine their targets and potency of action (ie, antibacterial versus anti-neoplastic). This is why there are thousands of studies done on all these minute variations of the quinolone scaffold, to see how that might change the basic drug from an anti-bacterial drug, to an anti-viral drug, to an anti-fungal drug, or to an anti-neoplastic drug. Again, on paper, it all looks good. But in practice, these delineations are not a rock solid given, as evidenced by the growing number of people recognized to have FQT/FQAD. They’re also not a rock solid given in the research lab either, as you read through the following references.

Researchers who study these antibiotics can never, ever say, with 100% certainty, that any of the FQ antibiotics currently on the market will not possibly “crossover” to affect your topoisomerase enzymes.   To the contrary, numerous research studies have revealed under what circumstances that might happen.   The “crossover” and “toxicity” potential of these drugs are like a nagging mosquito that just won’t stop buzzing around the head. The fact that FQs are targeting topoisomerase enzymes in general as a major mechanism of action is like a nagging voice in the back of everyone’s mind, wondering just how much “crossover” from bacterial to human topoisomerases might actually be occurring.

Regardless of the mechanism, FQT/FQAD victims are an increasingly growing and vocal proof that these drugs are dangerous. FQ-topoisomerase induced human DNA damage from double stranded DNA breaks, resulting in cell death or disabling mutations, simply cannot be ruled out as a potential cause or contribution to FQT/FQAD. Although there is a long history of these severe reactions to the FQ antibiotics, keep in mind that before the internet, there was no way to reliably recognize these reactions. And Pharma was certainly not about to advertise them either. So although much of the literature you read will defend the “safety” of FQ’s as anti-bacterial agents based on the assumption that they are “only targeting bacterial topoisomerases”, if you carefully read between the lines, you’ll begin to notice the circumstances and exceptions as to when that “might not be true”. And as far as I’m concerned, FQT/FQAD victims are the living “in vivo” proof of that as well.

“Crossover” of FQ antibiotics from bacterial to human topoisomerases is a real possibility.   Below are just a few of the published references available.  Print these out for your doctors, to hand to them along with the “FQ as Cancer Drugs” references.  I’ve also included at least one reference showing FQ interaction with human helicase, another enzyme necessary for DNA replication.    I’m also providing the first reference “How to Calculate the Dose of Chemotherapy”, because  a) it certainly applies to the FQs, and b) describes how easily toxicity can occur due to genetic variations in metabolism .

How to Calculate the Dose of Chemotherapy. “Despite the recent advances in anticancer treatment and the promise of novel targeted therapies, it is likely that cytotoxic chemotherapy will continue to be used for the next few decades. It is now recognized that our current method of dose calculation for chemotherapy using body surface area (BSA) is inaccurate. This method does not account for the marked interpatient variation in drug handling that is known to exist for these drugs so that drug effects such as toxicity are also highly variable and therefore unpredictable . . . Typically there is a 4–10-fold variation in cytotoxic drug clearance between individuals due to differing activity of drug elimination processes related to genetic and environmental factors. For example, the activity of cytochrome P450 (CYP) 3A4/5, the major oxidising enzymes for many cytotoxic drugs varies by as much as 50-fold. A common single-nucleotide polymorphism (SNP) or CYP3A5 has recently been identified and others are being searched for. In addition many drugs and disease states are known to inhibit or induce CYP activity further adding to this variation. Another example is the eight-fold variation in dihydropyrimidine dehydrogenase (DPD) activity, the enzyme that catabolises 5FU. Less is known about the variation in other critical hepatic elimination processes such as active biliary excretion by multidrug resistance gene 1 (MDR1), multidrug resistance-associated protein 2 (MRP2) and the other ATP binding cassette (ABC) family of efflux pumps, although some polymorphisms have been identified. A number of SNPs have also recently been identified for the steroid and xenobiotic receptor (SXR), a common-pathway receptor which transcriptionally activates a number of the drug elimination genes such as CYP3A4, MRP2 and MDR1. Variation in renal function is more easily identified but none of these complex processes are accounted for when BSA alone is used to calculate drug dose.”

Fluoroquinolones: relationships between structural variations, mammalian cell cytotoxicity, and antimicrobial activity.   “Fluoroquinolones are potent inhibitors of bacterial topoisomerase II (DNA gyrase). They can also inhibit eukaryotic topoisomerases, which could possibly lead to clastogenicity and/or cellular toxicity. Recent studies have demonstrated a correlation between mammalian cell cytotoxicity of the fluoroquinolones and the potential of these compounds to induce micronuclei, a genetic toxicity endpoint.   In an effort to identify potent nontoxic quinolone antibacterials, we have examined the structural features of the fluoroquinolones associated with mammalian cell cytotoxicity. An investigation of a wide variety of substituents at the 1, 5, 7, and 8 positions of a quinolone nucleus was conducted. The results indicate that no one position has a controlling effect on the observed cytotoxicity. Instead, a combination of the various substituents contributes to the effects seen.”

Relationship of cellular topoisomerase IIα inhibition to cytotoxicity and published genotoxicity of fluoroquinolone antibiotics in V79 cells.   “Fluoroquinolone (FQ) antibiotics are bacteriocidal through inhibition of the bacterial gyrase and at sufficient concentrations in vitro, they can inhibit the homologous eukaryotic topoisomerase (TOPO) II enzyme. FQ exert a variety of genotoxic effects in mammalian systems through mechanisms not yet established, but which are postulated to involve inhibition of TOPO II enzymes.”

The quinolone family: from antibacterial to anticancer agents.   “Indeed, a distinctive feature of drugs based on the quinolone structure is their remarkable ability to target different type II topoisomerase enzymes. In particular, some congeners of this drug family display high activity not only against bacterial topoisomerases, but also against eukaryotic topoisomerases and are toxic to cultured mammalian cells and in vivo tumor models. Hence, these cytotoxic quinolones represent an exploitable source of new anticancer agents . . . Their ability to bind metal ion co-factors represents an additional means of modulating their pharmacological response(s). Moreover, quinolones link antibacterial and anticancer chemotherapy together and provide an opportunity to clarify drug mechanism across divergent species.”

Nonclassical biological activities of quinolone derivatives. “Recently, quinolones have been reported to display “nonclassical” biological activities, such as antitumor, anti-HIV-1 integrase, anti-HCV-NS3 helicase and -NS5B-polymerase activities . . . Indeed, quinolones’ antimicrobial action is distinguishable among antibacterial agents, because they target different type II topoisomerase enzymes. Many derivatives of this family show high activity against bacterial topoisomerases and eukaryotic topoisomerases, and are also toxic to cultured mammalian cells and in vivo tumor models. Moreover, quinolones have shown antiviral activity against HIV and HCV viruses. In this context the quinolones family of drugs seem to link three different biological activities (antibacterial, anticancer, and the antiviral profiles) and the review will also provide an insight into the different mechanisms responsible for these activities among different species . . . While quinolone-based drugs have been developed extensively as antimicrobial agents (targeted to DNA gyrase, the prokaryotic counterpart of topoisomerase II), these studies provided evidence that quinolones may have potential as antineoplastic drugs. When comparing the known sequences of topoisomerases from bacteria to mammals, the sequences appear to be similar around active site tyrosine, not only among type II topoisomerase but also among type I. They also share the same mechanism of cell killing which is performed by trapping topoisomerase II in an intermediary cleavable complex with DNA, termed the “cleavable complex,” which is detected as DNA double strand breaks.”

Type II topoisomerases–inhibitors, repair mechanisms and mutations.   “Although the fluoroquinolone concentrations required in vitro to form a cleavage complex with native eukaryotic type II topoisomerase are 100- to 1000-fold higher than those required for gyrase, site-directed mutagenesis of a few critical residues can increase the sensitivity of human topoisomerase II to fluoroquinolones.”

Genotoxicity of topoisomerase II inhibitors: an anti-infective perspective.   “At present, an inevitable consequence of a chemical’s inhibitory activity on key regulators of DNA topology in bacteria, the type II topoisomerases, is a less pronounced effect on their eukaryotic counterparts. In the context of anti-infectives drug development, this may pose a risk to patient safety as inhibition of eukaryotic type II topoisomerases (TOPO II) can result in the generation of DNA double-strand breaks (DSBs), which have the potential to manifest as mutations, chromosome breakage or cell death. The biological effects of several TOPO II inhibitors in mammalian cells are described herein; their modulation of DSB damage response parameters is examined and evidence for the existence of a threshold concept for genotoxicity and its relevance in safety assessment is discussed.”

Evaluating the genotoxicity of topoisomerase-targeted antibiotics.   “Antibiotics like fluoroquinolones (FQs) that target bacterial type II topoisomerases pose a potential genotoxic risk due to interactions with mammalian topoisomerase II (TOPO II) counterparts. Inhibition of TOPO II can lead to the generation of clastogenic DNA double-strand breaks (DSBs) that can in turn manifest in mutagenesis . . . When applied to a class of novel bacterial type II topoisomerase inhibitors (NBTIs) . . .identified 22/27 NBTIs that induced >6-fold relative mutation frequency (MF) . . . Moreover, . . . using this approach suggested that these NBTIs, primarily of the H class, operated via a TOPO II poison-like mechanism of action (MoA) similar to FQs . . . These findings were corroborated through inspection of human TOPO IIα IC(50) data as NBTIs exhibiting equivalent inhibitory capacities had differing genotoxic potencies.”

Effects of quinolone derivatives on eukaryotic topoisomerase II. A novel mechanism for enhancement of enzyme-mediated DNA cleavage. “These findings strongly suggest that these quinolone derivatives represent a novel class of topoisomerase II-targeted drugs which have potential as antineoplastic agents.”

Type II topoisomerases as targets for quinolone antibacterials: turning Dr. Jekyll into Mr. Hyde.   “In addition to the antibacterial quinolones, specific members of this drug family display high activity against eukaryotic type II topoisomerases, as well as cultured mammalian cells and in vivo tumor models. These antineoplastic quinolones represent a potentially important source of new anticancer agents and provide an opportunity to examine drug mechanism across divergent species.”

Quinolone action against human topoisomerase IIa: stimulation of enzyme-mediated double-stranded DNA cleavage. “Several important antineoplastic drugs kill cells by increasing levels of topoisomerase II-mediated DNA breaks . . . Conversely, compounds such as quinolones are believed to stimulate the forward rate of topoisomerase II-mediated DNA cleavage.”

Design and synthesis of modified quinolones as antitumoral acridones.   “The bacterial topoisomerase II (DNA gyrase) and the mammalian topoisomerase II represent the cellular targets for quinolone antibacterials and a wide variety of anticancer drugs, respectively. In view of the mechanistic similarities and sequence homologies exhibited by the two enzymes, tentative efforts to selectively shift from an antibacterial to an antitumoral activity was made . . .”

Increased sensitivity to quinolone antibacterials can be engineered in human topoisomerase IIα by selective mutagenesis. “ . . . Mutations in human topoisomerase IIα have been generated in an attempt to engineer ciprofloxacin sensitivity into this enzyme . . . The triple mutation confers a three-fold increase in sensitivity to ciprofloxacin in vitro and similar sensitivities to a range of other quinolones . . . We have therefore shown the importance of this region in determining the sensitivity of topoisomerase II to drugs and have engineered increased sensitivity to quinolones” (My note: mutations in this region in those of us with FQT/FQAD should be looked for).

Synthesis, cytotoxicity and topoisomerase II inhibitory activity of lomefloxacin derivatives.   “A novel series of amide derivatives of lomefloxacin were synthesized and evaluated for their topoisomerase I and II inhibitory activity as well as cytotoxicity against a panel of five human cancer cell lines. Of the compounds prepared compounds 9d and 9g exhibited strong inhibition against topoisomerase II at 100μM.”

New insight for fluoroquinophenoxazine derivatives as possibly new potent topoisomerase I inhibitor.   “Fluoroquinolones, represented by ciproxacin and norfloxacin, are well-known clinical antimicrobial agents, and their phenyl ring expanded quinophenoxazines are reported as possible antitumor active compounds. These quinophenoxazines are known to inhibit DNA topoisomerase II essential for cell replication cycle. But there were no reports for topoisomerase I inhibition study for these compounds. In this report, we have prepared a few quinophenoxazine analogues and tested their topoisomerases I and II inhibitory activities and cytotoxicity. From the result, we found that quinophenoxazine analogues possessed strong topoisomerase I inhibitory capacity as well as topoisomerase II inhibition.”

Cytotoxicity of quinolones toward eukaryotic cells. Identification of topoisomerase II as the primary cellular target for the quinolone CP-115,953 in yeast.     “The quinolone CP-115,953 (6,8-difluoro-7-(4-hydroxyphenyl)-1-cyclopropyl-4- quinolone-3-carboxylic acid) represents a novel mechanistic class of drugs with potent activity against eukaryotic topoisomerase II in vitro. Although the quinolone is highly toxic to mammalian cells in culture, its mechanism of cytotoxic action is not known. Therefore, yeast was used as a model system to determine whether topoisomerase II is the primary target responsible for the in vivo effects of CP-115,953. The quinolone was equipotent to etoposide at enhancing DNA breakage mediated by the Saccharomyces cerevisiae type II enzyme. Moreover, at concentrations as low as 5 microM, CP-115,953 was cytotoxic to yeast cells that carried wild type topoisomerase II (TOP2+) . . . These results strongly suggest that topoisomerase II is the primary physiological target responsible for quinolone cytotoxicity and that CP-115,953 kills cells by converting the type II enzyme into a cellular poison.”

Effects of novel fluoroquinolones on the catalytic activities of eukaryotic topoisomerase II: Influence of the C-8 fluorine group.   “A previous study demonstrated that novel 6,8-difluoroquinolones were potent effectors of eukaryotic topoisomerase II . . . Removal of the C-8 fluoro group decreased the ability of the quinolone to enhance enzyme-mediated DNA cleavage approximately 2.5-fold . . . Removal of the C-8 fluorine reduced the ability of the quinolone to inhibit topoisomerase II-catalyzed DNA relaxation . . . These results demonstrate that the C-8 fluorine increases the potency of quinolone derivatives against eukaryotic topoisomerase II and mammalian cells. Further comparisons of CP-115,955 with CP-115,953 and CP-67,804 (the N-1 ethyl-substituted derivative of the difluoro parent compound) indicate that the two intrinsic activities of quinolone-based drugs towards topoisomerase II (i.e., enhancement of DNA cleavage and inhibition of catalytic strand passage) can be differentially influenced by alteration of ring substituents. Finally, correlations between the biochemical and cytological activities of these drugs suggest that the ability to inhibit catalytic strand passage enhances the cytotoxic potential of quinolones towards eukaryotic cells.”

Ciprofloxacin is an inhibitor of the Mcm2-7 replicative helicase.   “Most currently available small molecule inhibitors of DNA replication lack enzymatic specificity, resulting in deleterious side effects during use in cancer chemotherapy and limited experimental usefulness as mechanistic tools to study DNA replication. Towards development of targeted replication inhibitors, we have focused on Mcm2-7 (minichromosome maintenance protein 2–7), a highly conserved helicase and key regulatory component of eukaryotic DNA replication. Unexpectedly we found that the fluoroquinolone antibiotic ciprofloxacin preferentially inhibits Mcm2-7 . . .the discovery that fluoroquinolones can inhibit the eukaryotic helicase may explain some of the cytotoxic effects observed with ciprofloxacin and other fluoroquinolones. Our finding that the mcm4chaos3 allele confers resistance to ciprofloxacin supports our hypothesis that the Mcm2-7 complex is a ciprofloxacin target in cells and suggests that it could also be contributing to the deleterious side effects seen with this class of compounds”.



The “Overdose Hypothesis”:   Supratherapeutic or Increasing Concentrations of FQs Increase the Probability of FQ-Interaction With Human Proteins:  Using Topoisomerase as an Example. 

Given that “FQ – crossover” from bacterial topoisomerase to human topoisomerase reactions is a possibility, what are some circumstances that could be hypothesized under which this scenario might occur?

One possibility is that unique genetic polymorphisms might exist in our human nuclear or mitochondrial topoisomerases in those of us with FQT/FQAD which might increase our susceptibility to FQ antibiotics. With this scenario, FQ’s “could not distinguish” between bacterial topoisomerases and our own, leading to “crossover reactions”.   I suggested and discuss this hypothesis in “Topoisomerases — The Obvious Targets“.

The above hypothesis might be particularly relevant when it comes to mitochondrial topoisomerases (or any other mitochondrial enzymes, transporters, receptors, etc). It is generally accepted that ancient bacteria are the long lost ancestors of current day mitochondria living within our cells. When it comes to FQ’s, mitochondria may therefore “look like bacteria” in any number of ways, including similar topoisomerases . This makes them a prime target for the FQ’s and “crossover reactions” in general, and is the basis of “FQ-Induced Mitochondrial Toxicity”. For references, scroll down to “Mitochondria – Target for Adverse Effect” on this page.   As a result of these findings, there is a petition for yet another Black Box Warning to be placed on the FQ class of drugs regarding mitochondrial toxicity, here:      The Southern Network on Adverse Reactions (SONAR) Citizen’s Petition.     Also see “Mitochondrial Damage and Depletion” for how I related mitochondrial problems to potential thyroid related problems.

Of all the potential hypothetical mechanisms for Fluoroquinolone Toxicity (FQT) which exist, probably one that would be at the top of my list would be what I call “The Overdose Approach”, also briefly mentioned in “Topoisomerases: The Obvious Targets”.  Put simply, we were overdosed with a drug known to be toxic in high concentrations, which includes targeting topoisomerases and acting as a chemotherapeutic agent.   Many people intuitively understand the “overdose” concept.   And even the phrase “Fluoroquinolone Toxicity” suggests we were poisoned with a toxic substance.  Those of us with FQT/FQAD didn’t take handfuls of pills all at once to get this “overdose effect”.  We didn’t take the drugs inappropriately.  We took them as directed by our doctors, in the supposed correct dose for us.  So why would we be overdosed?

Although some quinolones appear to be eliminated from the body unchanged, others are partially metabolized, and a few are completely degraded.  So some metabolism, creating a variety of quinolone metabolites, does occur for most FQs. It’s known that there can be very large variations in the way different people metabolize drugs due to Phase 1 and 2 metabolism and renal clearance/excretion, and the FQ’s are no different.  It’s also well known that in higher doses, or “supra-therapeutic” concentrations, FQ’s transition from being an antibiotic targeting “only bacteria” to an anti-neoplastic agent, targeting “faster growing cells”. Meaning, the higher the dose or concentration, the more likely these drugs are to start binding to human topoisomerases. At what point in any one person does this transition occur? The facts are, no one knows.

With “The Overdose Scenario”, one would start thinking about some of the possible genetic and epigenetic variations in individuals in regard to Phase I/II/III Drug Metabolism. With this scenario, unique genetic and epigenetic vulnerabilities in those of us with FQT/FQAD could result in varying degrees of decreased ability to metabolize these drugs appropriately.  Once “overdosed” with a “supra-therapeutic” dose, the “FQ-antibiotic” could transition to “FQ-anti-neoplastic” agent.   At that point in time, as I described above in “FQ’s as Cancer Drugs”, we develop some or all of the symptoms of a “chemo overdose” and more:  we “lose our hair and nails, are chronically nauseated and lose 20-50 pounds, have severely dry eyes, mouth, and skin, strange skin rashes, lose the ability to sweat, have permanent peripheral neuropathy, muscle aches, headaches, fatigue, endocrine and neuroendocrine symptoms, and “chemo brain”/ “brain fog” CNS symptoms during the acute stage or as delayed symptoms.  This is in addition to the well known but peculiar FQ-Induced adverse affect of targeting collagens, resulting in documented tendon pain and ruptures, detached retinas, and aortic aneurysms.” I myself took the “low dose” of 250 mg twice a day for a few days, and look what happened.

What may contribute to making this cycle particularly toxic, is that the FQ’s are also known to inhibit several Cytochrome p450 Phase 1 enzymes while on the drug, and of course, they are also promiscuously interacting with the additional targets on this page. As toxic accumulations of the FQ and/or metabolites build up in our system, inhibition of these additional enzymes could easily decrease or prevent our ability to metabolize many other endogenous metabolites as well.  This might include, for example, steroids, fatty acids, fat soluble vitamins, hormones, and other drugs or supplements metabolized by these CYPs.  This would have additional deleterious effects in a variety of ways, one of which might be epigenetic modifications leading to permanence.  I’ve wondered if there is even the possibility that the FQs, in high enough concentrations, might increasingly target an enzyme which inhibits its own metabolism, a rather frightening possibility.

Fluorouracil (5-FU), another cancer drug, is a relevant example of the “Overdose Hypothesis”.  A small number of people in the population have a genetic variation that can severely decrease their ability to metabolize this drug.  Therefore, an identical dose of 5-FU in one patient may result in an “effective overdose” in another.  5-FU toxicity can result in severe side effects, including “fatal events”. Every cancer patient considering treatment with this drug should therefore undergo genetic testing first.  Given that such testing is very simple to do and is available, I don’t know why that wouldn’t occur, although it happens (see Washington Post article, “Medical Mysteries:  Toxic Chemotherapy“). (Note: those of you who have done the 23andMe testing have this data). Studies should be done to look for possible genetic and epigenetic variations within the FQT/FQAD population that might turn a “normal dose” of FQ into an “overdose” and “chemo” dose of FQ in us.

Although for the most part I am focusing on FQs inhibiting topoisomerase enzymes, I suspect the FQs target any number of other DNA/RNA replication and repair enzymes as well.   For example, research shows FQ interacting with Tdp1 and a helicase, also both involved in DNA replication and repair (references provided on this webpage).   These interactions are much more likely to occur at supra-therapeutic, or “overdose” concentrations of the drugs.   Once one begins to look at all the promiscuous unintentional targets of these drugs (known ones are listed on this page and the next), it’s not hard to see why some of us were hit so hard.   Our DNA and other proteins never stood a chance.

I’d like to reiterate here again, as I have elsewhere throughout this website,  that individual genetic variations in the ability to metabolize FQ’s or any other drugs, does not absolve Pharma, FDA, or the medical profession from accountability and liability. It doesn’t matter if I or anyone else has a genetic predisposing factor or not:  Now that these reactions have clearly come to light, and with the “Genomic Revolution” in full swing, Pharma and FDA have the capability and responsibility to study these reactions, learn from them, identify whatever predisposing factors may exist, and appropriately warn the medical profession and the public.  And if they can’t do that, then these drugs should either be pulled from the market or at the very least, severely restricted the same way any other dangerous DNA-damaging toxic chemotherapy drug would be.  Anything less should be criminal.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.  But for anything and everyone else — why take the risk?


DMEx Genotype Panel:   Commercial drug metabolism genotyping panels are popping up for clinical use, but none that I know of are looking for any specific variations that might affect FQ metabolism.  For those of you who have done the 23andMe analysis, you might have some or all of this information available already. Studies need to be done on the FQT/FQAD population to look for possible variances anywhere in Phase I/II/III metabolism genes.

Information on Phase I/II/III Drug Metabolism mechanisms

Drug Metabolism by Areo Saffarzadeh.   Nice video series explanation of Phase I/II metabolism; click on “Show More” for the list of videos available or see his YouTube channel.

Here are some references on FQ metabolism.


Metabolism and the fluoroquinolones.   “Quinolones differ considerably with respect to the relative importance of nonrenal drug elimination mechanisms. The extent to which the fluoroquinolones undergo biotransformation in the liver ranges from approximately 50 percent for pefloxacin to about 6 percent for ofloxacin. Although glucuronide conjugates have been identified as minor metabolites for some agents, most metabolic reactions involving quinolones occur through microsomal oxidative mechanisms at the cytochrome P-450 site. These metabolic alterations involve the piperazinyl moiety and usually result in compounds with significantly less microbiologic activity than the parent drugs. Of particular importance is the varying extent of formation of the oxoquinolone metabolite with all fluoroquinolones except ofloxacin. Available evidence suggests that the inhibition of metabolism of drugs such as theophylline and caffeine by quinolones is related to the production of the oxoquinolone metabolite. With all antibiotics, differences in microbiologic activity and pharmacokinetics influence the choice of one agent over another for individual patient selection or consideration for hospital formulary inclusion. For the quinolones the degree and type of metabolism may be a strong factor in this selection process.”

Acyl Glucuronidation of Fluoroquinolone Antibiotics by the UDP-Glucuronosyltransferase 1A subfamily in human liver microsomes. “Acyl glucuronidation is an important metabolic pathway for fluoroquinolone antibiotics. However, it is unclear which human UDP-glucuronosyltransferase (UGT) enzymes are involved in the glucuronidation of the fluoroquinolones. . . . These results demonstrate that UGT1A1, 1A3, and 1A9 enzymes are involved in the glucuronidation . . .”

Selective role of sulfotransferase 2A1 (SULT2A1) in the N-sulfoconjugation of quinolone drugs in humans.   “N-Sulfoconjugation is a common metabolic pathway of amine compounds in vivo. In the present study, we investigated the N-sulfation of quinolones and other amine drugs (ciprofloxacin, moxifloxacin, garenoxacin, desipramine, and metoclopramide) to assess the contribution of specific human cytosolic sulfotransferases (SULTs) to the reactions using purified recombinant enzymes and human liver cytosols (HLCs). Among the enzymes examined, human (h) SULT2A1 exhibited N-sulfoconjugation activities toward all drugs tested, whereas the other five different forms (hSULT1A1, hSULT1A3, hSULT1B1, hSULT1C2, and hSULT1E1) showed no detectable activities except hSULT1A1 for garenoxacin sulfation . . . The sulfating activities of HLCs toward the amines were well correlated with those for O-sulfation of dehydroepiandrosterone, a hSULT2A1 probe substrate. Taken together, the present results unequivocally demonstrate that hSULT2A1 is responsible for the N-sulfation of quinolones and possibly other therapeutic drugs in humans.”

Organic Anion Transporter 3 (Oat3/Slc22a8) Interacts with Carboxyfluoroquinolones and Deletion Increases Systemic Exposure to Ciprofloxacin.    “Renal secretion is a major determinant of their systemic and urinary concentration, but the specific transporters involved are virtually unknown. In vivo studies implicate the organic anion transporter (OAT) family as a pivotal component of carboxyfluoroquinolone renal secretion . . . The present findings also suggest that mOat3 contributes significantly to the distribution of ciprofloxacin in both genders, but its role in total clearance is more overt in females . . . These observations are consistent with a role for the basolateral organic anion exchangers Oat1 and Oat3 in the renal uptake of carboxyfluoroquinolones (ie, Cipro and Levo) . . . Despite more than two decades of investigation into carboxyfluoroquinolone transport, the specific interaction of carboxyfluoroquinolones with organic anion transporters has not been examined using heterologous expression systems. Accordingly, we investigated the interaction of the two major renal basolateral organic anion transporters, Oat1 and Oat3, with ciprofloxacin and other carboxyfluoroquinolones . . . While renal secretion of carboxyfluoroquinolones is well accepted as a major route of elimination, the specific transport mechanism for this pathway remains ambiguous. Thus far, investigators have suggested possible roles for organic anion, organic cation, and undetermined transporter families, expressed on both basolateral and apical plasma membranes . . . The promiscuous interaction of carboxyfluoroquinolones with various transport systems stems from their zwitterionic nature, bearing both amine and carboxylate moieties on opposite ends . . . Although a role for an individual organic anion transporter in carboxyfluoroquinolone renal secretion has not been reported, three in vivo studies in particular provide substantial evidence that the OAT family plays a pivotal role . . . The present results indicate that carboxyfluoroquinolones, especially ciprofloxacin, exhibit a significant interaction with murine and human Oat3/OAT3 . . . Furthermore, ciprofloxacin interacts with mOat3/hOAT3 selectively, demonstrating no inhibition of mOat1/hOAT1, and no transport by mOat1, the other major renal basolateral transporter . . . Therefore, it is likely that OAT3 plays a significant role in humans in the renal secretion of carboxyfluoroquinolones. Thus, the clear role of mOat3 in carboxyfluoroquinolone elimination, along with the lack of interaction with mOat1/hOAT1, and previous reports of hOAT3 polymorphisms yielding non-functional hOAT3 protein, suggest there is a human population that may respond poorly to carboxyfluoroquinolone therapy when prescribed for eradication of renal and post-renal pathogens . . . Finally, two putative ciprofloxacin metabolites were observed during HPLC analysis, both of which were completely absent in spiked plasma standards and early time points, but highly evident in later time points (Fig. 7). Each of the suspected metabolites exhibited heightened accumulation in Oat3(-/-) mice (Figs. 7 and and8),8), suggesting that ciprofloxacin levels are not elevated as a result of impaired metabolism in Oat3(-/-) mice, but rather as a consequence of perturbed secretory transport. For both genotypes, the metabolites accumulated to a greater extent in females. Additionally, the late-eluting metabolite was markedly heightened in female Oat3(-/-) mice compared to wild-type or males of either genotype (Fig. 8B) . . . Four ciprofloxacin metabolites have been identified in humans, desethyleneciprofloxacin (M1, or the 2-aminoethylamino metabolite), sulfociprofloxacin (M2), oxociprofloxacin (M3), and formylciprofloxacin (M4) (Zeiler et al., 1987). The M1 and M3 metabolites have also been observed in animals (rats and monkeys) (Siefert et al., 1986). All of these metabolites retain the carboxylate moiety, suggesting that they may also be substrates for Oat3 . . . The late-eluting (8.5 minute) HPLC peak does not appear to correspond to any of the previously reported metabolites (M1-M4) of ciprofloxacin. Further studies are required to positively identify the compound represented by this peak . . . In conclusion, the results of this investigation show that renal basolateral mOat3/hOAT3 interacts with carboxyfluoroquinolones in vitro, and the murine ortholog plays a significant role in ciprofloxacin elimination at clinically observed concentrations in vivo. In contrast, mOat1/hOAT1 does not interact with ciprofloxacin, indicating that this other major renal basolateral OAT is not involved in elimination of ciprofloxacin. Therefore, hOAT3 polymorphisms, some of which have already been demonstrated as highly dysfunctional (Erdman et al., 2006), should be considered a potential source of variable carboxyfluoroquinolone efficacy in tissues and especially throughout the urinary tract. Furthermore, numerous drug interactions involving carboxyfluoroquinolones, whether impacting the carboxyfluoroquinolone level or concomitant drug level, likely occur via competition for transport on hOAT3. Such carboxyfluoroquinolone-drug interactions have been documented in humans and are known to involve substrates/inhibitors which have been demonstrated to interact with mOat3 in vivo (e.g., methotrexate (VanWert and Sweet, 2007) and probenecid). Pharmacotherapeutic OAT3 substrates, e.g., penicillin G and non-steroidal anti-inflammatory drugs, should therefore be administered with caution in patients who are receiving a carboxyfluoroquinolone for a urinary tract infection, as blood and tissue levels of the quinolone may be therapeutic or supertherapeutic, while urinary levels may fail to reach the minimum effective concentration.”

Fluoroquinolone (ciprofloxacin) secretion by human intestinal epithelial (Caco-2) cells.    “The major route of elimination of the fluoroquinolone anti-biotic ciprofloxacin is via the kidneys.  However, there is extensive evidence for a significant trans-intestinal elimination of ciprofloxacin.  Since biliary elimination accounts for less than 1% of an intravenous dose and only a minor component of ciprofloxacin in faeces is metabolites, this suggests the existence of a specific intestinal secretory mechanism for ciprofloxacin . . . The substrate specificity of the ciprofloxacin secretory transport in Caco-2 epithelia is distinct from both the renal organic anion and cation transport. A role for P-glycoprotein in ciprofloxacin secretion may also be excluded.   A novel transport mechanism, sensitive to both DIDS and verapamil mediates secretion of ciprofloxacin by human intestinal Caco-2 epithelia.”

Identification of influx transporter for the quinolone antibacterial agent levofloxacin.   “Several ATP-binding cassette transporters are involved in efflux transport of these agents, but no influx transporters have yet been molecularly identified . . . organic anion transporting polypeptide 1A2 (OATP1A2 (OATP-A), SLCO1A2) was concluded to transport levofloxacin . . . OATP1A2 is likely to function as a high-affinity transporter. The inhibitory effects and the expression of transport activity of other quinolone antibacterial agents suggested that OATP1A2 commonly transports all the agents tested.  In conclusion, this is the first identification of an influx transporter for fluoroquinolones, and the results suggest that active influx transport at least partially explains the high membrane permeability of the quinolone agents in various tissues.

The inhibitory effects of fluoroquinolones on L-carnitine transport in placental cell line BeWo.   “L-Carnitine plays an important role in lipid metabolism by facilitating the transport of long-chain fatty acids across the mitochondrial inner membrane followed by fatty acid beta-oxidation. It is known that members of the OCTN family play an important role in L-carnitine transport in the placenta. Investigation of drug-drug or drug-nutrient interaction in the placenta is important for establishment of safety drug medication during pregnancy. The aim of this study was to determine the effects of fluoroquinolones, inhibitors of OCTN2, on L-carnitine transport in the placenta which is known to have a high expression level of OCTN2. We investigated the inhibitory effect of five fluoroquinolones, ciprofloxacin (CPFX), gatifloxacin (GFLX), ofloxacin (OFLX), levofloxacin (LVFX) and grepafloxacin (GPFX), on L-carnitine transport mediated by OCTN2 in placental cell line BeWo cells. We found that all of the fluoroquinolones inhibited L-carnitine transport, GPFX being the strongest inhibitor. We also found that the inhibitory effects of LVFX and GPFX depended on their existence ratio of zwitterionic forms as, we reported previously. Furthermore, we elucidated the LVFX transport mechanism in BeWo cells. LVFX was transported actively by transporters. However, we found that LVFX transport was Na+-independent and l-carnitine had no inhibitory effect on LVFX transport, suggesting that LVFX acts as inhibitor of OCTN2, not as a substrate for OCTN2.”

Mechanism of the inhibitory effect of zwitterionic drugs (levofloxacin and grepafloxacin) on carnitine transporter (OCTN2) in Caco-2 cells.   “L-Carnitine plays an important role in lipid metabolism by facilitating the transport of long-chain fatty acids across the mitochondrial inner membrane followed by fatty acid beta-oxidation. It is known that L-carnitine exists as a zwitterion and that member of the OCTN family play an important role in its transport. The aims of this study were to characterize L-carnitine transport in the intestine by using Caco-2 cells and to elucidate the effects of levofloxacin (LVFX) and grepafloxacin (GPFX), which are zwitterionic drugs, on L-carnitine uptake . . . Experiments on the inhibitory effect of LVFX and GPFX on L-carnitine uptake showed that LVFX and GPFX inhibited L-carnitine uptake more strongly at pH 7.4 than at pH 5.5. It was concluded that the zwitterionic form of drugs plays an important role in inhibition of OCTN2 function.”

Fluoroquinolone disposition: identification of the contribution of renal secretory and reabsorptive drug transporters.   “Fluoroquinolones (FQs) exist as charged molecules in blood and urine making their absorption, distribution, and elimination likely to be influenced by active transport mechanisms. Greater understanding of in vivo FQ clearance mechanisms should help improve the predictability of drug–drug interactions, enhance the clinical safety and efficacy, and aid future novel drug design strategies.   The authors present an overview of FQ development and associated drug–drug interactions, followed by systematic quantitative review of the physicochemical and in vivo pharmacokinetic properties for 15 representative FQs using historical clinical literature. These results were correlated with in vitro studies implicating drug transporters in FQ clearance to link clinical and in vitro evidence supporting the contribution of drug transport mechanisms to FQ disposition. Specific transporters likely to handle FQs in human renal proximal tubule cells are also identified. Renal handling, that is, tubular secretion and reabsorption, appears to be the main determinant of FQ plasma half-life, clinical duration of action, and drug–drug interactions. Due to their zwitterionic nature, FQs are likely to interact with organic anion and cation transporters within the solute carrier (SLC) superfamily, including OAT1, OAT3, OCT2, OCTN1, OCTN2, MATE1, and MATE2. The ATP-binding cassette (ABC) transporters MDR1, MRP2, MRP4, and BCRP also may interact with FQs.”

ASSESSMENT OF THE ROLE OF SOLUTE CARRIER DRUG TRANSPORTERS IN THE SYSTEMIC DISPOSITION OF FLUOROQUINOLONES: AN IN VITRO – IN VIVO COMPARISON.   “Fluoroquinolones (FQs) are broad-spectrum charged antimicrobials exhibiting excellent tissue/fluid permeation. Thus, FQ disposition depends essentially on active transport and facilitative diffusion. Although most early transporter studies investigating renal elimination of FQs have focused on apical efflux of FQs from renal proximal tubule cell (RPTC) into urine, their basolateral uptake mechanism(s) from blood into RPTC (i.e., first step to tubular secretion) has not yet been explored in detail. Renally expressed SLC22 members: organic anion (OATs) xiv and cation (OCTs) transporters are known to transport such small organic ionic substrates (molecular weight ~400 Da). Hence it is of interest to explore the role of these basolateral transporters in renal elimination of FQs, and to further quantitatively assess their impact in clinically observed FQ drug-drug interactions (DDI).”

Ciprofloxacin Is Actively Transported across Bronchial Lung Epithelial Cells Using a Calu-3 Air Interface Cell Model.   “This study has clearly shown that ciprofloxacin is a substrate for active transport in the air interface Calu-3 cell model and suggests the involvement of OCTs, OATP2B1, and MRPs as transporters. Importantly, this has implications with respect to the delivery of ciprofloxacin antibiotics by inhalation treatment and also possible drug-drug interactions. Hence, further studies on expression levels and functional properties are required to better understand the clinical relevance of these drug transporter interactions.”

Quinolone pharmacokinetics and metabolism.   “The pharmacokinetic properties of the new fluoroquinolones are characterized by a high volume of distribution, long biological half-life, low serum protein binding, elimination by renal and extrarenal mechanisms with high total and renal clearances, limited biotransformation and moderate to excellent bioavailability after oral administration. However, each quinolone derivative (ciprofloxacin, enoxacin, fleroxacin, norfloxacin, ofloxacin and pefloxacin) possesses individual pharmacokinetic parameters, which should be considered in the treatment of patients, especially when liver or renal dysfunction exists.”

Pharmacokinetics of quinolones in renal insufficiency.   “The pharmacokinetics of the new fluoroquinolone derivatives have been extensively studied in patients with various degrees of chronic renal insufficiency during the last few years. Their kinetic profiles depend on the elimination pathways and on the degree of metabolic transformation. Renal insufficiency does not significantly modify pefloxacin kinetics. For the other new quinolones, a decrease in glomerular filtration rate below 20-30 ml/min induces an increase in terminal half-life and a decrease in plasma and renal clearance, related to the degree of renal impairment. These drugs are poorly removed by haemodialysis. Dosage adjustments are required, particularly in severe renal failure and for the drugs almost exclusively excreted, in unchanged form, via the renal route.”

Metabolism and Disposition of Novel Des-Fluoro Quinolone Garenoxacin in Experimental Animals and in Interspecies Scaling of Pharmacokinetic Parameters.   “Garenoxacin is a novel quinolone that does not have a fluorine substituent at the C-6 position in the quinoline ring. Garenoxacin or14C-garenoxacin was intravenously or orally administered to rats, dogs, and monkeys. Metabolic profiles and pharmacokinetic parameters were investigated focusing on the species differences and the allometric scaling of pharmacokinetic parameters. . . . The major metabolic routes for garenoxacin were phase II metabolism. The principal metabolite commonly observed in rats, dogs, and monkeys was the sulfate of garenoxacin (T-3811M1). Another common metabolic pathway in all animals tested was the conjugation of the carboxylic acid substituent (formation of M6), which is similar to previous reports . . . In a previous study, garenoxacin did not undergo metabolism in human microsomes and did not inhibit the activities of several cytochrome P450 enzymes in human microsomes (Furuhata et al., 2000). Garenoxacin is probably metabolized to only a limited extent by cytochrome P450 in all species including humans and undergoes mainly phase II metabolism. Of the other minor routes of metabolism observed for garenoxacin in all species tested, the formation of the carbamoyl glucuronide (M2) is a novel route for the basic moiety at position C-7 of the quinoline ring. It is speculated that M2 was formed from subsequent glucuronide conjugation of carbamic acid (M3) . . . In summary, characteristics of the metabolism and disposition of garenoxacin were common across species. Garenoxacin underwent phase II metabolism and the metabolites were excreted into the bile, whereas unchanged garenoxacin was excreted into the urine.”

Fluoroquinolones influence the intracellular calcium handling in individuals susceptible to malignant hyperthermia.    “The mechanisms of fluoroquinolone-induced myotoxicity are unknown but an involvement of intracellular calcium handling is suspected. An in vitro contracture test used to investigate cellular processes in malignant hyperthermia (MH) can be applied to study the effects of fluoroquinolones . . . Fluoroquinolones appear to have a pathological influence on intracellular calcium handling. A pre-existing impairment of the calcium homeostasis, however, seems to be necessary for this behavior.”

Metabolic effects as a cause of myotoxic effects of fluoroquinolones.   “FQs influence skeletal muscle metabolism. Myotoxic effects of FQs can, therefore, be explained by an influence on the cellular energy balance. . . . FQs interfere with mitochondrial ATP production, and can potentially cause intracellular energy depletion. Elevated resting intracellular calcium levels result in a higher cellular energy consumption. Exposure to various substances can lead to a hypermetabolic syndrome via calcium release from the SR.[9] A fluorine moiety is an integral part of both volatile anesthetics and FQ. Covalently bound fluorine interferes with the RYR resulting in an increased calcium release. In addition, a reduced calcium transport back into the SR can be considered as a further potential reason for increased intracellular calcium levels. Prior studies have shown that covalently bound fluorine is capable of inhibiting the sarcoplasmic calcium ATPase (SERCA).[16] An inhibition of SERCA leads to higher intracellular calcium concentrations. This corresponds with recent in vitro results that indirectly measured elevated intracellular calcium levels after exposure to FQs.[17] Calcium, as a second messenger, activates energy consuming processes. Both the direct inhibition of the mitochondrial aerobic capacity, and the influence on the cellular calcium homeostasis, leads to a disruption of the cellular energy balance. A depletion of energy reserves results in muscle cell breakdown and explains myotoxic properties. With elevated intracellular calcium as an important pathway for FQ-induced myotoxicity dantrolene, an intracellular calcium inhibitor might attenuate FQ-induced tissue damage. This behavior could be proven for other substances.[14,18].”

Metabolism and excretion study of DW116, a new fluoroquinolone, in rats.   “Metabolite identification and urinary and biliary excretion of the new fluoroquinolone antibacterial agent DW116 [1-(5-fluoro-2-pyridyl)-6-fluoro-7-(4-methyl-1-piperazinyl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid, hydrochloride] after oral administration have been studied in Sprague-Dawley rats. The excretion kinetics were monoexponential. Most of the drug was eliminated via the hepatic and renal routes. Mean renal clearance of DW116 was 73.4 ml/hr/kg and mean biliary clearance was 83.8 ml/hr/kg. The major metabolite excreted in the bile was identified as the glucuronide ester of the parent drug using base-hydrolysis of the conjugate metabolite followed by co-HPLC with standard compound,¹⁹F-NMR and LC-MS methods. The glucuronide conjugate was also found in urine. The mean urinary recoveries of free and total (free plus glucuronide ester) DW116 were 28.6±2.7% and 36.4±1.8% of the administered dose and the corresponding biliary recoveries were 14.4±5.5% and 37.0±7.6%, respectively.”

Fluoroquinolone Efflux Mediated by ABC Transporters.   “Quinolones and fluoroquinolones are broad spectrum bactericidal drugs, which are widely used in both human and veterinary medicine. These drugs can quite easily enter cells and are often used to treat intracellular pathogens. Some fluoroquinolones have been reported to undergo efflux, which could explain their low bioavailability. There is a growing need to understand resistance mechanisms to quinolones, involving for instance mutations or the action of efflux pumps. Several members of the ATP-binding cassette (ABC) drug efflux transporter family (MDR, MRP, ABCG2) significantly affect the pharmacokinetic disposition of quinolones. Active secretory mechanisms common to all fluoroquinolones have been suggested, as well as competition between fluoroquinolones at transporter sites. For grepafloxacin and its metabolites, MRP2 has been demonstrated to mediate biliary excretion. However, MDR1 is responsible for grepafloxacin intestinal secretion. Recently it has been shown that ciprofloxacin and enrofloxacin are efficiently transported ABCG2 substrates which are actively secreted into milk. It appears that multiple ABC transporters contribute to the overall secretion of fluoroquinolones. The objective of this work is to review the recent advances in insights into ABC transporters and their effects on fluoroquinolone disposition and resistance including data on drug secretion into milk.”

Characterization of the Interactions between Fluoroquinolone Antibiotics and Lipids: a Multitechnique Approach.   “Probing drug/lipid interactions at the molecular level represents an important challenge in pharmaceutical research and membrane biophysics. Previous studies showed differences in accumulation and intracellular activity between two fluoroquinolones, ciprofloxacin and moxifloxacin, that may actually result from their differential susceptibility to efflux by the ciprofloxacin transporter . . . All together, differences of ciprofloxacin as compared to moxifloxacin in their interactions with lipids could explain differences in their cellular accumulation and susceptibility to efflux transporters. . . . Since their discovery in the early 1960s, the quinolone group of antibacterials has generated considerable clinical and scientific interest including the development of the second-generation quinolones like ciprofloxacin. These wide spectrum drugs are characterized by the introduction of fluor into position C-6 on the molecule. Progressive modifications in their chemical structure have resulted in improved breadth and potency of in vitro activity and pharmacokinetics (1). The most significant developments have been enhancement of the therapeutic potential of fluoroquinolones thanks to liposomal encapsulation (2., 3., 4.) and improved anti-Gram-positive activity of the newer compounds like moxifloxacin (5).Due to their ability to accumulate inside phagocytes (1., 6., 7., 8.), fluoroquinolones are also useful for eliminating facultative intracellular pathogens that resist phagocytic death. We recently showed that fluoroquinolones accumulate in macrophages and show activity against a large array of intracellular organisms including Listeria monocytogenes and Staphylococcus aureus(9). Quite significant differences among closely related derivatives have been observed with the following ranking in cellular accumulation and intracellular activity: ciprofloxacin < levofloxacin < garenoxacin < moxifloxacin (9). So far, to our knowledge, this has not received satisfactory explanation. Characterization of fluoroquinolones uptake by eukaryotic cells suggested that both passive diffusion and active transport systems are involved. The transbilayer diffusion of fluoroquinolones has been demonstrated (10) and our group reported that ciprofloxacin, but not moxifloxacin, is subject to constitutive efflux in J774 macrophages through the activity of an MRP-related transporter (11).Drug/lipid interactions can modulate not only translocation of the drug through the natural membranes but also its interaction with efflux proteins (12., 13.). In this respect, it is well known that 1), substrates have to be transported from the lipid bilayer to the transporter protein before a capture mechanism of the drug by the inner leaflet of the cytoplasmic membrane (14); and 2), the activity of transporter is critically dependent on the surrounding lipid bilayer environment (15., 16.), which may be modified by drugs. In view of the critical role of lipids for the drug cellular uptake and differences observed for two closely related compounds, ciprofloxacin and moxifloxacin (Fig. 1), we investigated the interactions of these two fluoroquinolones with lipids, using an array of complementary techniques. For both ciprofloxacin and moxifloxacin, atomic force microscopy (AFM) reveals an erosion of dipalmitoylphosphatidylcholine (DPPC) domains within dioleoylphosphatidylcholine (DOPC) fluid phase while Langmuir studies show a condensing effect. Further molecular studies show that fluoroquinolones can 1), exchange from lipids to aqueous phases (phase transfer and molecular modeling studies); 2), decrease the all-trans conformation of lipid acyl chain (attenuated total reflection Fourier transform Infra-Red (ATR-FTIR)); and 3), increase the lipid disorder (ATR-FTIR). When the effects of the two fluoroquinolones are compared, it clearly appears that moxifloxacin has a higher condensing effect related to a lower propensity to be released in the aqueous phase from lipid monolayer and to a higher ability to decrease the all-trans conformation of lipid acyl chain without marked effect in lipid-chain orientation. All together, differences of ciprofloxacin as compared to moxifloxacin in their interactions with lipids can be related to differences in their cellular accumulation and therefore activity against intracellular bacteria . . . Taken together, our data suggest that ciprofloxacin and moxifloxacin interact in a very different way with lipids. The major challenge, however, is to understand the mechanism, at a molecular level, unraveling the interaction between lipids and fluoroquinolones and the path of these antibiotic molecules through lipid layers . . . All together, we showed that the condensing effect of fluoroquinolones on lipid layer resulted not only from a dissolving mechanism but also from an alteration of the intramolecular acyl-chain order in relation to a reduction in trans-gauche isomerization about the carbon-carbon bonds, and change in the average molecular tilt of lipid acyl chain of DPPC. The two fluoroquinolones investigated showed difference in their effects. Ciprofloxacin had a lower ability to decrease the all-trans conformation of lipid chains than moxifloxacin but showed a higher capacity to affect the orientation of lipid chains and to disorder the membrane. These effects might explain its higher ability to be released from the lipid monolayer to aqueous phase and its lower effect on surface pressure-area isotherms of monolayers. In contrast, moxifloxacin has a lower capacity to induce membrane disorder and does not change the tilt between the molecular axis and the transition dipole moment. Moxifloxacin has also a higher tendency to decrease the number of all-trans conformations with increase of kink, creating a pocket in which moxifloxacin can be located. This can explain why the amount of moxifloxacin in the aqueous phase was lower than that found for ciprofloxacin and why the mean molecular area of lipids/fluoroquinolones monolayers after compression is significantly lower in the presence of moxifloxacin as compared to ciprofloxacin.”

Quinolone levels in serum and maxillofacial tissues under ibuprofen co-administration following surgical trauma. (Google title for link)   “Quinolone concentrations in serum and in most of the tissues were significantly higher in the experimental groups compared to the controls. However, the co-administration of ibuprofen caused a higher increase of the quinolone levels in the control animals than in the experimental groups.   Summarizing the ibuprofen effect, two actions can be distinguished: 1) Displacement of quinolones from their binding site and 2) Impairment of renal excretion through the decreased blood flow. Furthermore, it is suggested that quinolones inhibit the p-aminohippurate transport (PAH) system across the renal tibuli32, while ibuprofen affects the same system33. In response to these mechanisms, accumulation of quinolones is observed in serum and tissues. Therefore, upon co-administration with ibuprofen, quinolone levels are increased in control animals, more pronounced in serum, whereas this enhancement is less evident under stress.”

Effects of substituents on the NMR features of basic bicyclic ring systems of fluoroquinolone antibiotics and the relationships between NMR chemical shifts, molecular descriptors and drug-likeness parameters.  (Google title for link)  “Relationships between 1H- and 13C-NMR chemical shifts of fluoronaphthyridone and fluoroquinolone ring systems, calculated molecular descriptors (MDs) and drug-likeness scores (DLSs), computed for monoprotonic cations of investigated fluoroquinolone salts (TVAH+, PFXH+ and CIPH+), were also explored. The topological polar surface area (TPSA), the parameter of lipophilicity (miLogP), the relative molecular mass (Mr) and the volume (V) of computed molecular descriptors (MDs), as well as the G protein-coupled receptor ligand-likeness (GPCR ligand-ls), the ion channel ligand-likeness (ICL-ls), the kinase inhibitor-likeness (KI-ls) and the nuclear receptor ligand-likeness (NRL-ls) were used in this study . . . The structures of fluoroquinolones are directly reflected in their pharmacological effect and side-effect profiles. In addition to the b-keto-carboxylic group of the quinolone bicyclic ring system at positions 3 and 4, fluoroquinolones possess a fluorine atom at position C6. While the b-keto-carboxylic group is responsible for the basic pharmacological activity and acts as a binding site, the fluorine atom is responsible for cell penetration and gyrase affinity. Other substituents, positioned at N1 and C7, are responsible for the overall potency and antibacterial spectrum, and position X8 (X = N) for the antianaerobic spectrum. However, changes in the basic fluoroquinolone pharmacophore moiety as well as changes in substituents lead to unexpected adverse reactions, such as the CNS reactions, drug-drug interactions, phototoxicity, hepatotoxicity and cardiotoxicity such as QTc interval prolongation of electrocardiogram, which have been reported in clinical evaluations or the post-marketing surveillance of several new quinolones (7). Similarly, as found for the pharmacological effect, the relationships of the structure and adverse effects were observed and specific substituent side effects were revealed (11, 13).”



Tdp1 (Tyrosyl-DNA Phosphodiesterase):  Target for Cancer

Our bodies are nothing short of miraculous.   Every single moment that we’re alive, billions and billions of minute reactions have to occur with exquisite perfection and fidelity to keep us alive.  This includes repairing DNA damage.  One of the enzymes involved in repairing DNA damage is called Tdp1.   Note that Tdp1 is a phosphodiesterase enzyme.

DNA damage is a normal daily occurrence in our lives, due to a variety of factors. For example, as described in the paper “The DNA Cleavage Reaction of Topoisomerase II: Wolf in Sheep’s Clothing”,  some foods consumed in the human diet actually contain naturally occurring topoisomerase II poisons.  These include the bioflavonoids, which are components of many fruits, vegetables and plant leaves, EGCG, a component of green tea, and genistein, which is prominent in soy (as a matter of interest, the ring structure of genistein is remarkably similar to that of quinolones and is a topo poison; a significant number of FQT/FQAD flox victims develop a sensitivity to soy and soy products post flox).   The toxic metabolite of acetaminophen (NAPQI) is also a potent topoisomerase II poison that can cause liver failure.  And of course there are many concentrated synthetic compounds, including the fluoroquinolone antibiotics, that are also potent topoisomerase inhibitors which create DNA damage.   It’s estimated that DNA damage due to environmental factors and normal metabolic processes inside the cell occurs at an astounding rate of 10,000 to 1,000,000 molecular lesions per cell per day.

So nature has provided a way for our DNA to repair itself with several types of DNA repair enzymes and mechanisms.   These mechanisms work well as long as the insult, or damage, to the DNA isn’t too overwhelming.   Our bodies and cells are designed to deal with the much less concentrated amounts of natural topo inhibitors found in foods such as fruits and vegetables, green tea and soy.  For the most part, people don’t “overdose” on these foods, although several accounts of “green tea toxicity” have occurred (1, 2 ).  My guess would be, someone sensitive to green tea or soy, probably shouldn’t take an FQ.  Soy was never a large part of my diet, although when I did eat it, I never experienced any sensitivities, and I’ve never even tried green tea, so I don’t know whether or not I would have been sensitive to that.

Unfortunately, taking an FQ antibiotic is a huge concentrated form of a topoisomerase poison taken at any dose, way more than one would get in any foods. For people who may have a genetic or epigenetic sensitivity or inability to metabolize these antibiotics, or may have a genetic vulnerability in some of these “DNA repair” enzymes, toxicity could occur quite easily.

FQs, as topoisomerase poisons, damage DNA.  Once that happens, cells will gallantly and valiantly try to repair that DNA damage in an effort to “save their lives” with enzymes like Tdp1.    And that includes cancer cells.   So the idea behind using FQs to target Tdp1 is that if the cells manage to survive the first hit with a topoisomerase poison, go after the repair enzymes next, as a “double whammy”.

FQs not only function as topoisomerase poisons, but as Tdp1 inhibitors as well.  They not only damage DNA, but damage the repair mechanism too.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.  But for anything and everyone else — why take the risk?


Phosphodiesterase as a Target for Cancer Therapeutics. “Investigators at the National Cancer Institute have discovered fluoroquinolone derivatives as specific Tdp1 inhibitors that could potentiate the pharmacological action of Top1 inhibitors currently used in cancer treatment.”

Fluoroquinolone Derivatives as Inhibitors of Human Tyrosyl-DNA Phosphodiesterase (Tdp1)   Chemotherapy can provide therapeutic benefits in many cancer patients, but it often ultimately fails to cure the disease since cancer cells can become resistant to the chemotherapeutic agent. To overcome these limitations, additional strategies are needed to restore or amplify the effect of antitumor agents. Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is a DNA repair enzyme involved in the repair of DNA lesions created when the activity of the Topoisomerase 1 (Top1) is inhibited. Tdp1 has been regarded as a potential therapeutic co-target of Top1 in that it seemingly counteracts the effects of Top1 inhibitors, such as camptothecin. By reducing the repair of Top1-DNA lesions, Tdp1 inhibitors have the potential to augment the anticancer activity of Top1 inhibitors.   The NIH investigators discovered fluoroquinolone derivatives as specific Tdp1 inhibitors that could potentiate the pharmacological action of Top1 inhibitors, which are currently used in cancer treatment. The instant invention discloses a method of treating cancers with a therapeutically effective amount of a Top1 inhibitor, and a fluoroquinolone derivative that inhibits Tdp1 activity.”

Fluoroquinolone derivatives or sulfonamide moiety-containing compounds as inhibitors of tyrosyl-dnaphosphodiesterase (TDP1).   “A method for treating cancer in a subject, comprising administering to a subject having cancer a therapeutically effective amount of (i) a fluoroquinolone derivative that inhibits tyrosyl-DNA-phosphodiesterase 1 (Tdp1) activity or (ii) a sulfonamide moiety-containing compound that inhibits tyrosyl-DNA-phosphodiesterase 1 (Tdp1) activity, thereby treating the cancer in the subject. In certain embodiments, the fluoroquinolone derivative or sulfonamide moiety-containing compound is co-administered with a topoisomerase I (TopI) inhibitor.”


MicroRNA (miRNA): Target for Cancer

A relative newcomer to the cancer research scene are microRNAs (miRNAs).   They are also intriguing for their potential as “biomarkers” for specific diseases, including autoimmune, CFS/ME, Fibromyalgia, and others as well as cancers.   Recently, specific miRNAs have been found circulating in our bloodstream, which opens the door to a possible easy testing method for specific diagnostic markers of numerous conditions.

A microRNA is a small non-coding RNA molecule found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression.   Small non-coding RNAs comprise several classes and sizes, of which miRNA is one, but all share a unifying function in cellular physiology:   epigenetic regulation of gene expression.   An important distinction to make is that miRNAs do not alter the DNA nucleotides or genetic code; they are an “epigenetic” form of regulation.   Whereas topoisomerase and Tdp1 inhibitors have the capability of altering the genetic DNA code directly via DNA damage, miRNA’s do not, which is why they are called an “epigenetic modification”.

MicroRNA’s have the ability to “turn off”, inhibit, or silence gene expression.  They also can “turn on” or enhance gene expression.   But miRNAs are a relatively recent discovery, and for the most part, this has been based on their “silencing” function.    For the non-science people reading this, the thing to keep in mind is, increases in miRNA usually mean decreases in expression of one or more proteins.   When it comes to cancer cells, this property is of definite interest.  If you can increase miRNAs, you can decrease cell growth by cutting off important nutrients the cell needs.   In other words, if you can increase miRNAs enough, you may be able to decrease or kill cancer cells.

It turns out that an FQ antibiotic, Enoxacin, does just that.   Ciprofloxacin and Norfloxacin were also found to have miRNA enhancing activity, although not as much as Enoxacin.

Of course, if you have cancer, you once again might want this property of FQs.   But for those of us who don’t have cancer and never had cancer, this is yet one more potential onslaught on our normal cells, the ones we need to survive and thrive normally.   If you have read this far, then hopefully you’re beginning to see a pattern here.   FQs effectively “slow down”, “inhibit”, “decrease” or “stop” cell growth, survival, proliferation, and migration in a variety of ways.   As a result, FQs can permanently kill cancer cells.   But they can permanently kill normal cells via the same mechanisms too.    And for some of us, the permanent altering or death of those cells appears to translate into a lifetime of disability and suffering with FQT/FQAD.

In those of us with permanent FQT/FQAD, I think we’re essentially “missing” one or more important proteins, most likely an enzyme, either due to permanent genetic or epigenetic silencing.   Since I was a completely normal and healthy person the day before taking the antibiotic, I can only assume that either a) an actual de novo genetic mutation has occurred, b) more likely an epigenetic silencing of an important metabolizing enzyme has occurred, or c) both occurred as a result of taking the FQ.

In cancer, there is “too much” of everything: “too much growth too fast”, “too much blood supply”, a gene “turned on”.  In those of us with FQT/FQAD, I think the opposite is occurring:  we have “too little growth”, “too little blood supply”, a gene “turned off”.   This is what one would expect to happen if a chemo drug was blasting normal, healthy cells in supra-therapeutic amounts.   If we are missing an important enzyme necessary for metabolism, then toxic metabolites would “build up” or increase, resulting in our symptoms.  I discuss this concept more in the CYP1A2/3A4 section (see Part 2, next page).

Additionally, when a catastrophic loss of one or more enzymes occurs, the cells and body try to compensate by increasing collaterally acting enzymes and proteins.  It seems to me, that permanent overexpression of these compensatory enzymes or proteins could actually result in formation of neoplastic properties, including cancer.

Note that viral microRNAs play an important role in the regulation of gene expression of viral and/or host genes to benefit the virus.   Viruses can manipulate the cellular processes necessary for their replication by targeting the host (meaning your) RNAi machinery.   Therefore, miRNAs play a key role in host–virus interactions and pathogenesis of viral diseases.   This may be one link to consider between “Post-Viral, Post-FQ, and Post-Chemo reactions”.

Debilitating fatigue is often a major symptom in FQT/FQAD, and is a hallmark of CFS/ME. In this recent CFS/ME study, significant upregulation of a few miRNAs were found as potential biomarkers.  I wonder if this chronic miRNA overexpression is resulting in chronic underexpression of important enzymes or proteins needed by our cells to function normally.  I discuss an example of this concept in “Thyroid Damage Due to Collagen/Connective Tissue Damage”, (scroll down about ¾ of the page), where downregulation of a specific protein occurs due to increased expression of a specific miRNA.    As a matter of interest, another recent CFS/ME study found that of the 20 metabolic pathways found with abnormalities, eighty percent of the diagnostic metabolites were decreased.  This is in keeping with my suggestion that those of us experiencing FQT/FQAD with a severe chronic fatigue component are “missing” or have decreased expression of some important fundamental proteins necessary for quality of life.

Micro-RNAs are thought to “fine tune” gene expression and therefore play an important role in “homeostasis”.    As with everything else in the body, having just the right amount of miRNA – not too much, and not too little – is important for overall homeostasis.   Having the “right amount” of miRNA appears to also play an important role in preventing cancer and overexpression of proteins.  But having “too much”, just like having “too little”, is detrimental.    FQs, including Ciprofloxacin, appear to alter the balance of miRNAs.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.   But for anything and everyone else — why take the risk?


MicroRNAs and other non-coding RNAs as targets for anticancer drug development.   “Another example is the small molecule enoxacin, a fluoroquinolone that is used as an antibacterial compound, which has been shown to enhance the production of a subset of miRNAs by binding to the miRNA biosynthesis protein TAR RNA-binding protein 2 (TARBP2)63. Treatment of RKO and HCT116 colon cancer cells with enoxacin caused an overall upregulation of miRNA expression in vitro. Enoxacin treatment increased the expression of 24 mature miRNAs in mice and reduced tumour growth in xenograft, orthotopic and metastatic mouse models63. Interestingly, the drug’s growth-inhibitory effect was substantially compromised both in a colon cancer cell line with an inactivating mutation in the TARBP2 gene and in in vivo studies with TARBP2‑deficient mice63, which indicates that miRNA regulation by enoxacin is the main mecha­nism for its anticancer effect. These examples highlight the key role of disrupted miRNA expression patterns in cancer and demonstrate the effectiveness of fully restoring the distorted spectrum of miRNAs that are downregulated in cancer cells”.

Small molecule enoxacin is a cancer-specific growth inhibitor that acts by enhancing TAR RNA-binding protein 2-mediated microRNA processing.      “MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression at the posttranscriptional level and are critical for many cellular pathways. The disruption of miRNAs and their processing machineries also contributes to the development of human tumors. A common scenario for miRNA expression in carcinogenesis is emerging that shows that impaired miRNA production and/or down-regulation of these transcripts occurs in many neoplasms. Several of these lost miRNAs have tumor-suppressor features, so strategies to restore their expression globally in malignancies would be a welcome addition to the current therapeutic arsenal against cancer. Herein, we show that the small molecule enoxacin, a fluoroquinolone used as an antibacterial compound, enhances the production of miRNAs with tumor suppressor functions by binding to the miRNA biosynthesis protein TAR RNA-binding protein 2 (TRBP). The use of enoxacin in human cell cultures and xenografted, orthotopic, and metastatic mouse models reveals a TRBP-dependent and cancer-specific growth-inhibitory effect of the drug. These results highlight the key role of disrupted miRNA expression patterns in tumorigenesis, and suggest a unique strategy for restoring the distorted microRNAome of cancer cells to a more physiological setting.”

MicroRNA: a prognostic biomarker and a possible druggable target for circumventing multidrug resistance in cancer chemotherapy.     “Apart from exhibiting aberrant expression of a few miRNAs, human cancers are in fact characterized by impaired miRNA processing and global miRNA dysregulation. It has been recently shown that miRNA expression can be differentially altered by xenobiotic drugs in difference human cell lines. The drugs identified are not necessarily anticancer drugs. The practical implication is that they could be safely administered with other conventional anticancer drugs in an attempt to reverse miRNA-mediated drug resistance. Along this line of investigation, the fluoroquinolone class of antibiotics has been shown to enhance RNA interference and promote miRNA processing. This may represent a novel approach to modulate multiple miRNAs simultaneously or to restore the global miRNA expression (i.e. micRNAome) to provide a cancer-specific growth inhibitory effect.”

miRNA-based therapies: Strategies and delivery platforms for oligonucleotide and non-oligonucleotide agents.      “A number of fluoroquinolone antibiotics were shown to enhance the effect of siRNAs and miRNAs through interaction with the RNAi machinery. The most potent compound, enoxacin, was further studied for the molecular mechanism of this effect.  Enoxacin was found to increase the binding affinity of TRPB, an integral component of the RISC, to miRNA precursors.  As such, there is of course no specificity for certain miRNA sequences.  Because the global miRNA expression is significantly lowered in tumours, a general increase of miRNA activity may nevertheless be an attractive option in oncology.  Indeed, enoxacin reduced cell viability in cancer cell lines.”

Enhancement of RNAi by a small molecule antibiotic enoxacin.   “Our longstanding interest in drug-nucleic acids interaction 5 led us to search for potential small molecular regulators of RNAi. We hypothesized that inhibitors of RNA helicases may increase the stability of double-stranded siRNA, so as to enhance RNAi efficiency. Since a large family of fluoroquinolone antibiotics target bacterial DNA gyrase complexed with the targeted DNA possibly in A-form (similar to RNA) and since they also exhibit antiviral activity through interference with Tat-TAR interaction 7, we decided to screen a library of commercially available fluoroquinolone antibiotics, with the hope that some of the analogs may cross-inhibit relevant human RNA helicases. Herein, we report that enoxacin, one of the fluoroquinolone antibiotics known to inhibit bacterial gyrase and topoisomerase IV with minimal effects on their mammalian counterparts, can increase RNAi efficiency. We have found that enoxacin can reduce the concentrations of siRNA by 2~5-fold for the same RNAi knockdown efficiency . . . In summary, we have demonstrated that certain fluoroquinolone antibiotics such as enoxacin, in addition to their powerful clinic use for the treatment of infections in humans and animals, can be used to increase RNAi efficiency. The precise mechanism of this RNAi enhancement remains unclear at present. While our manuscript was in preparation, a similar finding with more detailed analysis was reported by Jin and colleagues, who proposed that enoxacin acts by potentially increasing RISC loading efficiency through a mechanism depending on the protein factor TRBP. Nevertheless, one cannot rule out the possibility that the effect of enoxacin on RNAi is due to the cross-interaction with human RNA helicases and the stabilization of RNAi molecules, especially in view of the finding that human RNA helicase A (RHA) is an active RISC component and functions in RISC as an siRNA loading factor.”

A new tool for in vivo manipulation of brain microRNA levels: the work of Smalheiser et al.   “Fluoroquinolones are an interesting family of small molecules that exhibit a number of bioactive properties; enoxacin not only interacts with TAR RNA-binding protein 2 (TARBP2) to promote Dicer activity but also alters V-ATPase binding to actin, JNK signaling, and cytochrome P450 activities, as well as inhibiting prokaryotic DNA gyrases . Interest in enoxacin has been renewed by cancer microRNA profiling, which revealed wide-scale reductions in expression, including the loss of many tumor-suppressor microRNAs.  As potent down-regulators of messenger RNA abundance and translation, microRNAs target a majority of genes in the human genome and thus represent a global, and potentially druggable, regulatory mechanism capable of affecting most molecular networks.”

Enoxacin Elevates MicroRNA Levels in Rat Frontal Cortex and Prevents Learned Helplessness.   “MicroRNAs (miRNAs) are a class of small non-coding RNAs that control gene expression by modulating translation, mRNA degradation or stability of mRNA targets. The role of miRNAs in disease pathophysiology is emerging rapidly. Enoxacin, a fluoroquinolone used clinically as an anti-bacterial compound, enhances the production of miRNAs in vitro and in peripheral tissues in vivo, but has not yet been tested as an experimental tool to study the relation of miRNA expression to neural functions or behavior.”

A small molecule enhances RNA interference and promotes microRNA processing.   “RNAi is a well-conserved mechanism that uses small noncoding RNAs to silence gene expression post-transcriptionally. Gene regulation by RNAi has been recognized as one of the major regulatory pathways in eukaryotic cells. The endogenous small RNAs can shape diverse cellular pathways, including chromosome architecture, development, growth control, apoptosis and stem cell maintenance . . . To test whether the quinolone family in general acts to enhance the RNAi pathway, we examined the effects of several other quinolones, both commercially available and synthetically modified molecules (enoxacin-V1–3), using our RNAi GFP reporter system. We found that two of these compounds (ciprofloxacin (Cipro) and norfloxacin (Noroxin)) have substantial RNAi-enhancing activity . . . These results suggest that enoxacin promotes the processing and loading of siRNAs/miRNAs onto RISCs by facilitating the interaction between TRBP and RNAs in mammalian cells . . . To determine whether enoxacin has similar effects in vivo, we tested it in a GFP transgenic mouse line . . . These results suggest that enoxacin enhances siRNA-mediated mRNA degradation in vivo.”

Enoxacin inhibits growth of prostate cancer cells and effectively restores microRNA processing.   “Remarkably, enoxacin was able to decrease cell viability, induce apoptosis, cause cell cycle arrest, and inhibit the invasiveness of cell lines. Enoxacin was also effective in restoring the global expression of miRNAs.   This study is the first to show that prostate cancer cells are highly responsive to the anti-tumoral effects of enoxacin. Therefore, enoxacin constitutes a promising therapeutic agent for prostate cancer.”


HIF1a (Hypoxia-Inducible Factor 1-alpha):   Target for Cancer

HIF1 alpha is a protein heavily involved in responding to low oxygen levels (called “hypoxia) within cells.   Rapidly growing cancer cells need increased nutrients to supply their needs, and this includes oxygen.   Cancer cells need these extra nutrients, oxygen and an extra blood supply to grow faster than “normal” cells, to form tumors, and to spread.   Therefore, anything that slows down, inhibits, or stops cell growth, survival, proliferation, and migration, or prevents cells from using resources such as glucose, oxygen, or blood supply, can function as a cancer drug.

Cancer cells often express higher levels of HIF1a than normal cells in order to meet their excessive growth requirements.   HIF1a activates the transcription of more than 100 target genes (and possibly many hundreds)  that are involved in crucial aspects of cancer biology, including angiogenesis (increased blood supply), cell survival, glucose metabolism and migration/invasion.   Additionally, typically, the more HIF1a there is, the more aggressive and less responsive to treatment the cancer is.   Therefore, inhibiting HIF1a is an attractive goal for cancer therapy.   If you can inhibit HIF1a, you can decrease cell growth by cutting off numerous important nutrients the cells needs.   In other words, if you inhibit HIF1a enough, you may be able to decrease or kill cancer cells.

It turns out that FQ antibiotics such as Ciprofloxacin, Enrofloxacin, and Norfloxacin, may do just that.   To date, there is only one recently published study that I could find, but I think it’s an important one.

In this study using kidney cell cultures, FQs, in concentrations considered therapeutic, abolished HIF1a protein.    Remember, HIF1a activates more than 100, and possibly many hundreds, of other target genes involved in providing cells with basic life support in the form of nutrients the cell needs.    By abolishing HIF1a, a cascade effect ensues and multiple other nutrients the cell needs to survive and function are abolished too.

Although this is an attractive goal for cancer cells, it would be catastrophic for all the other normal cells in your body.   In fact, this has been a limitation in the cancer research so far to find a useful HIF1a inhibiting drug which is more selective, and wouldn’t have such broad based effects.   If this is happening in FQT/FQAD victims, this could certainly account for the devastating multiplicity of symptoms many of us feel, with a loss of homeostasis at a very important fundamental cellular and mitochondrial level.  This includes “drastic effects on vascularization and energy metabolism in connective tissues, contributing to decreased blood flow in an already hypoxic and avascular tissue” (see abstract below).   Disruption of “oxygen homeostasis” mechanisms is serious business.

Interestingly (at least from my point of view), I originally came across HIF1a from a symptoms approach.   In several places on this website, I described the massive “flares” I was experiencing for a time.   Here’s a description of one of them:

In a split second, its starts.   I feel like I have a momentary almost-blackout, and then the massive “dump and thump” in my chest:   it feels like the “substance” – hormones, neurotransmitters, whatever it is, starts or hits my chest and heart, with a big thump of my heart, and then literally starts flowing through my veins, through my body, down through my legs, as if I’ve just gotten an intravenous injection.   I start breathing hard, break out into a cold drenching sweat, heart is racing and pounding in my chest, and there is severe “tightness” and chest pain; my legs and feet become ice cold at the same time the severe burning starts in my muscles.   When it slams into my brain, I almost go down, it feels like a truck has hit me from the side, and the feeling of intense “impending doom” and “this is it” hits me along with the vertigo.    I’ve learned to get down on my hands and knees, or at least grab the wall, because standing is too dangerous and I might collapse.  The pulses of the “substance” continue, like waves, for a few seconds more, and my symptoms worsen with each pulse, I’m horrifically cold, with severe nausea and chills, my legs are burning, and as the reaction continues, my whole body becomes neurologic with that “electric fence” buzzing feeling.    Once again, I know I am dying.  Unfortunately, it’s not true; I never do.   As much as this feels like a heart attack, it isn’t.   After it’s over, I’m left with the aftermath:  severe CNS symptoms of head pressure and pain, ear pain, severe eye pain and dryness, diaphragm muscles feel weak making it hard to breathe, leg muscles are weak, ice cold, and burning, making it hard to walk, severe pain in glands under the jaw, thyroid area feels swollen and painful, difficulty swallowing, jaw muscles severely painful with shooting neuro pains, all tendons hurt.  The weakness in my muscles is so severe in this aftermath that I cannot walk more than a few steps, I tremble and shake when attempting to stand, and even holding my head up is hard.  I have to wait until this “substance” metabolizes off, which will start in several hours if I don’t have another flare.  I also become aware that this “hit by a truck” feeling I experienced during the acute phase of my reaction is the original version of these “flares”. 

Unfortunately, I had plenty of opportunities to experience these and get to know the more subtle warnings within a fraction of second before the “substance” let loose.  I originally attributed this “substance” as being a T4/T3 “dump”, possibly from a thyroid adenoma (appropriate TH dose does attenuate or even eliminate these flares, so it is playing some kind of role).   However, I had a longer differential list which included pheochromocytoma (Pheo), paraganglioma (PGL), mast cell activation (MCA) /cytokine storm, acute porphyria, serotonin syndrome, a “Disulfiram-like” “aldehyde toxicity” reaction, or possibly a cholinergic crisis (some kind of ACh dump or accumulation).   Urine and blood tests while I was highly symptomatic appeared to rule out a pheochromocytoma and acute porphyria.   Multiple repeated testing ruled out parathyroid adenoma, but Multiple Endocrine Neoplasia had been on my list from the start.   Ultimately, for a number of reasons, paraganglioma (PGL) ended up at the top of the list for me.   I’ve never had any imaging done or a professional workup for PGL, but one thoracic MRI did not reveal any obvious or visible masses, and the SNP’s that 23andMe provided for PGL/Pheo-related were insignificant.   So even though my symptoms were indicative of a PGL/Pheo, the main question I had to ask myself was:   were these symptoms pathological due to a problem such as an adenoma, or were they really compensatory in nature, an appropriate response to a problem elsewhere?

Yes, the response felt horrifically dramatic, but I think there’s more going on in the above scenario than these hormonal/neurotransmitter “dumps”.   I also thought I had a receptor, transporter, or channelopathy issue going on as well, which meant I effectively felt these surges much more acutely than I normally would have.   This created a “double whammy” situation in terms of severity of symptoms.   Regardless, I came to think of these horrific “flares” as some sort of huge immediate compensatory effort to “right a wrong” somewhere.

As I said, I had plenty of opportunities to experience these flares, and to think about what was causing them or what was going on with me.   I began to notice the split-second, almost “blackout” type feeling in my brain before the “substance” let loose.  When I thought of these momentary transient feelings of “blacking out”, it almost felt like someone was choking me.   And that would mean lack of oxygen to the brain and body.  This is when I started thinking about “oxygen homeostasis” being a problem, which led me to HIF1a and other oxygen sensing mechanisms.   It felt like I’d have these momentary transient oxygen “blackouts”, with a compensatory huge sympathetic/catecholamine response a fraction of a second later.  I wondered if, without this dramatic compensatory response, I would have been essentially suffering multiple mini-strokes, and this was my body’s attempt to prevent that (although, quite frankly, it’s hard to think I haven’t had any permanent brain damage anyway as a result of all the FQ-Induced CNS symptoms I’ve suffered over the years).

I ultimately thought I did not have a PGL tumor as the cause of my symptoms, but that instead, I was having a very “PGL/Pheo” type response to abnormal or disrupted cellular changes in oxygen, carbon dioxide, or pH levels, especially in my brain.   I wondered if a problem existed with one of the sensing mechanisms for oxygen, which is what led me to consider HIF1a.   When the study came out in 2015 showing that in cells cultured in the lab, FQs suppressed HIF1a translation, it caught my eye.  Just because this happened in the lab doesn’t mean it’s happening in my body.  But given that from a symptoms approach alone, I had also arrived at HIF1a to consider as a possibility for damage, it doesn’t seem so coincidental.

There may be an association between HIF1a and Paragangliomas (PGLs), which are usually benign (non-cancerous) tumors of the cells that act as chemoreceptors located along blood vessels.  These cells, located in the carotid bodies of the neck and aortic bodies near the heart, detect changes primarily in oxygen, but they also sense changes in CO2 and pH.   They are therefore involved in very sensitive regulation of oxygen levels and acid-base homeostasis.  In most cells, HIF1a is constitutively expressed in low levels under normoxic conditions, however, under hypoxia, HIF1a is often significantly upregulated.  It turns out that PGL development may be associated with chronic hypoxia (low oxygen).  PGLs are more common in people and animals living at high altitude, and in people with chronic obstructive pulmonary disease and heart disease.   Therefore, there may be an association between HIF1a expression and PGL formation.   I don’t know if I had a PGL, as only a complete workup could rule that out, but I would put permanent epigenetic suppression or more likely disruption, of HIF1a synthesis on the “hypothesis list”.  Whatever’s going on with me, it feels like I’m not able to produce enough of it, fast enough, at the time I need it, and then, not able to metabolize it, or degrade it, fast enough, when I need that to happen too.   It feels like it’s a homeostasis problem, in this case, the protein of interest would be potential HIF1a involvement.

Another interesting observation I’d made is that I had personally known or read of several FQT/FQAD victims who had been diagnosed with some kind of glandular neuroendocrine tumor, or what I call, some kind of “ – oma”.   These tumors, called adenomas, are usually benign (non-cancerous), but they can produce some pretty debilitating symptoms if they are producing unregulated hormones.   I don’t know if there are any statistics available, but I know FQT/FQAD victims have been diagnosed with the following post FQ:    thyroid nodules (adenoma of the thyroid gland), parathyroid adenoma (adenoma of the parathyroid gland), thymoma (adenoma of the thymus gland), insulinoma (adenoma of the pancreas), and pheochromocytoma (adenoma of the medulla of the adrenal gland).    I don’t know if anyone’s been diagnosed with paraganglioma yet, but then, I doubt most clinicians would be even considering this.   When FQT/FQAD victims go to the ER with these symptoms, they are told they’re having a “panic attack” and given some benzos.

Many of these “ – omas” are derived from something call “neural crest cells”.   Many of my symptoms seem to read like a road map of neural crest cell (NCC) derivatives (See Wiki Neural Crest, and scroll down to “Cell Lineages” [Cranial, Trunk, Vagal, Cardiac] and “Neural Crest Derivatives” [Mesectoderm, Endocrine, Peripheral Nerves, Melanocytes].  Note how NCCD’s make up the connective tissue of the head and neck glands [thyroid, pituitary, thymus, salivary, lacrimal], tendons of ocular and masticatory muscles, dental related cells, peripheral nerves including of the head and neck, the catecholamine releasing chromaffin cells of the adrenal medulla, calcium regulating parafollicular cells of the thyroid, oxygen/carbon dioxide and pH sensing glomus cells in the carotid and aortic bodies, neurons of the olfactory nerve, etc.

As I said earlier, thyroid hormone does decrease or attenuate these “flare” reactions greatly.  There is a connection between TH (T3) and HIF1 activation indirectly via an RXR route  (1, 2).   I suppose this could be one consideration as to why I experience appropriate TH doses and serum levels as playing such a large role in attenuating or decreasing these “flares”.   See “Additional Mechanisms to Consider”, scroll to “Steroid Super Family Receptors/ HRE’s” for additional links connecting TH, RAR/RXR, and Neural Crest Cells.

As we have seen so far, FQs “slow down, inhibit, or stop cell growth, survival, proliferation, and migration, and prevent cells from using resources such as glucose, oxygen, or blood supply” in a variety of ways and via multiple mechanisms.   One of these ways may be via suppression of HIF1a translation, and I would hypothesize that neural crest cell derivatives, and labile stem cells, may be unintentional targets.   As to why adenomas would form, perhaps some cells still able to replicate are trying to compensate via overexpression of numerous substances for neighboring cells which are experiencing overall loss of nutrients.   Continued upregulation of HIF1a helps regenerate lost or damaged tissue.   If HIF1a is not appropriately regulated, normal cellular and tissue repair mechanisms could fail.

For those of us with permanent FQT/FQAD, it’s obvious that our cells and tissues are having a hard time regenerating and repairing themselves.   If FQs suppress HIF1a proteins, it could just be one more reason why.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.    But for anything and everyone else — why take the risk?


Nonantibiotic Effects of Fluoroquinolones in Mammalian Cells.   “ In contrast to these dramatic epigenetic changes consistent with the predicted effects of iron chelation on dioxygenases, we report an unpredicted result in the case of HIF-1α. Here, dioxygenase inhibition should stabilize HIF-1α by protecting it from prolyl hydroxylation. In dramatic contrast to this prediction, HIF-1α protein was eliminated by FQ treatment . . . It was completely unexpected that cells treated with CIPRO, ENRO, or NOR showed a profound decrease in HIF-1α and HIF-2α levels relative to controls.   Remarkably, HIF-1α and HIF-2α were suppressed in CIPRO-treated cells even upon co-treatment with DFO or CoCl2 in hypoxia . These results suggest that FQs exert suppressive effects on HIF-1α and HIF-2α protein levels upstream of regulated proteolysis . . . Combined with the prior observations that HIF-1α protein loss did not result from increased protein degradation, this result placed focus on suppression of HIF-1α mRNA translation in the presence of FQ. Evidence for such FQ-induced translation repression was observed in an experiment to measure new HIF-1α synthesis after metabolic labeling. Here, we observed that FQ treatment blocked new HIF-1α mRNA translation upon addition of methionine. Additionally, suppression of HIF-1α can have drastic effects on vascularization and energy metabolism in connective tissues, contributing to decreased blood flow in an already hypoxic and avascular tissue . . . Given their ability to inhibit dioxygenases, we report the unexpected and counterintuitive suppression of HIFα proteins by FQ. Although FQ inhibition of PHD enzymes marking HIF-1α and HIF-2α for destruction should stabilize these proteins, both HIF-1α and HIF-2α levels were dramatically decreased upon FQ treatment.  Hypoxia, DFO, or CoCl2 co-treatment was unable to overcome this suppression. We show that neither enhanced protein degradation nor decreased mRNA levels account for HIF-1α and HIF-2α suppression. Instead, we find that HIF mRNA translation is inhibited by FQ treatment. Future experiments will be necessary to explore pathways associated with translational suppression of HIF-1α synthesis.   To what extent are the present results relevant to therapeutic FQ doses?   CIPRO concentrations as low as 10 μm inhibited HIF mRNA translation.   Comparing these concentrations to physiological concentrations reported during FQ therapy, serum concentrations of CIPRO are 16 μm but can approach 1–3 mm in the kidneys of treated patients. Upon overdose, CIPRO concentrations in the urine are even higher. Our choice of human embryonic kidney cells to study FQ effects reflects the high kidney exposure upon FQ treatment. Indeed, acute renal failure is associated with high FQ concentration . . . Our unexpected observation of FQ-induced HIF-1α loss suggests the possible use of FQ drugs in cancer therapy.”


Dioxygenases: P4H (prolyl 4-hydroxylase), LH1 (lysyl hydroxylases), PHD (HIF-1α-prolyl hydroxylase dioxygenase), JMHD (Jumonji domain histone demethylases), TET1 (Tet methylcytosine dioxygenase 1):   Unintentional Targets / Adverse Effects

These are some hefty names for some pretty important enzymes needed for healthy collagen synthesis, and epigenetic modifications of DNA.   These enzymes were all found to be inhibited by FQs in the same study discussed above in “HIF1a:  Target for Cancer”.   To date, this is the only study I know of that has looked at the role of FQs interacting with these enzymes.

P4H and LH1 are enzymes that play central roles in collagen maturation and therefore structural integrity of tendons.   If these enzymes are inhibited or compromised in function, tendon structure and stability are compromised, potentially resulting in tendon tears and ruptures.

PHD is an oxygen sensing enzyme within cells that works in concert with HIF1a, which was covered in the section above.   Inhibiting PHD should result in increased HIF1a expression under normal circumstances.  However, the study revealed that even though PHD was inhibited by FQs, HIF1a was as well.  As was discussed in the section above, this was found to be due to suppressed translation of HIF1a, resulting in less HIF1a.

JMDH and TET1 are demethylase enzymes involved in DNA epigenetic effects.   In general, increased methylation acts to repress, or silence, gene transcription.    In other words, important proteins that cells need may be “turned off” when methylation occurs.    Demethylases, such as JMDH and TET1, can remove these methylations, and help “turn on” genes again.   However, FQs inhibit JMDH and TET1 demethylases, resulting in increased methylation of histones and DNA.

All of these enzymes are alike in that they require molecular oxygen, alpha-ketoglutarate (2KG), and iron (II) to work properly.   If any of these three substances are decreased or missing, the enzymes won’t function as much or at all.   In this way, these enzymes act as sensors of energy metabolism.   If oxygen is high or low, these enzymes respond in a compensatory manner.   Note that 2KG is an important intermediate in the TCA cycle which takes place in mitochondria.   FQs are unfortunately known to target and damage mitochondria via a variety of other mechanisms as well, increasing FQ-Induced mitochondrial toxicity overall.  In this in vitro study, it was found that decreases of these enzymes by FQs occurred in part (but not all) by FQ chelation of iron.  This is in keeping with FQ chelation of numerous divalent and trivalent cations, and presumably, the enzymes dependent on them.  Since there are a tremendous number of enzymes in our bodies which rely on minerals as cofactors, this potentially amounts to a tremendous amount of enzyme suppression, at least while on the FQ.

In this study, some, but not all, of these effects appeared reversible with iron supplementation.   However, when it comes to FQT/FQAD, keep in mind that plenty of people have been low on iron at some point in time in their lives.    Although they might become anemic, they don’t typically rupture tendons or develop FQT-like multi-symptom conditions as a result.   So although “iron poor blood” may play a role in some of us with FQT/FQAD, it isn’t the sole definitive factor.   This is where something like HIF1a translation suppression may play a potentially large role in FQT/FQAD, especially given the large number of genes driven by its expression.   Additionally, this is the first study to show global epigenetic changes induced by FQ antibiotics.  These changes of increased methylation, resulting in decreased gene expression of potentially hundreds or more genes, may be exacerbated by low iron and other mineral status during the acute phase of the reaction and may ultimately also contribute to the long term or permanent effects seen with FQT/FQAD.

So far in this very long write up, we’ve covered how FQs target a lot more than “just the bacteria” whenever these antibiotics are taken.  The list of human enzymes and proteins that they target, resulting in inhibition, suppression, or decreases in function, continues to grow.  With inhibition of HIF1a and demethylases, hundreds, if not thousands, of additional genes are likely suppressed during FQ use.

As a matter of interest, I have tried taking both alpha-ketoglutarate (about ¼ of a 350 mg capsule) and succinic acid (about 1/6 of a 500 mg capsule) supplements.   I had the strongest reaction with aKG, right where it counts, up in that “olfactory bulb/nasal sinuses” area, within a couple hours of taking it.   My “nasal sinuses” became extremely dry and painful, as if the moisture was being “squeezed” out of that area.    This pain and dryness extended to my eyes, and, it felt like, my brain was being “squeezed dry” too.   The characteristic phantosmia developed right along with this.   It was so painful, and such an obvious “block”, that I didn’t want to try it again.  I was able to tolerate the succinic acid for a couple of doses before starting with a similar, but not as strong, effect.   I said “right where it counts” because this olfactory/sinus area has obviously been damaged in me, as it’s been a large part of my symptoms, including the CNS ones, since this whole ordeal started.   According to the FDA Cipro drug insert, “tissue concentrations of Cipro often exceed serum concentrations in both men and women, and is present in active form in saliva, nasal and bronchial secretions, and mucosa of the sinuses (among others)” – all where I have experienced severe pain and dryness that is highly responsive to TH, foods, and supplements.   I have often thought that cell biopsies of the olfactory mucosa right up there by the olfactory bulb would reveal a lot about where the problems are with FQT/FQAD, including the CNS issues.    Also as a matter of interest, the “Phantosmia” page is one of the top read pages on this website, so there are a lot of people who experience this particular phenomenon.

There are a lot of dioxygenase enzymes, not just the ones in this study.  In “Additional Mechanisms to Consider“, I had listed TDO/IDO involved in tryptophan metabolism, and HGD, involved in Alkaptonuria (spontaneous tendon ruptures is one symptom), as potential targets to consider.   I am not a biochemist, but from what I can tell, FQs seem to potentially target oxidoreductases and enzymes involved in redox reactions, oxidases, monooxygenases, dioxygenases, dehydrogenases, hydroxylases, etc.  The list is long, and rather scary.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ. But for anything and everyone else — why take the risk?

Nonantibiotic Effects of Fluoroquinolones in Mammalian Cells.   “ Here we investigate the interaction of relevant concentrations of fluoroquinolone (FQ) antibiotics Ciprofloxacin (CIPRO), Norfloxacin (NOR), and Enrofloxacin (ENRO) with a cultured human embryonic kidney cell line, revealing previously unreported enzyme inhibition effects  that may explain toxicities associated with FQ treatment. We show that iron chelation by FQ leads to epigenetic effects through inhibition of α-ketoglutarate-dependent dioxygenases that require iron as a co-factor. Three dioxygenases were examined in HEK293 cells treated with FQ.   At sub-mM concentrations these antibiotics inhibited Jumonji domain histone demethylases, TET DNA demethylases, and collagen prolyl 4-hydroxylases, leading to accumulation of methylated histones and DNA, and inhibition of proline hydroxylation in collagen, respectively . . . We evaluated histone and DNA demethylation by the JMHD and TET1 families of dioxygenases, respectively.  These dioxygenases play roles in determining the epigenetic status of chromatin.  JMHD catalyzes the removal of methyl groups from histone tails.  Its inhibition leads to increased global histone methylation.  TET1 catalyzes the first step of cytosine demethylation.  Inhibition of TET1 results in global accumulation of 5-methylcytosine (5mC) in genomic DNA. . .To what extent are the present results relevant to therapeutic FQ doses?   A CIPRO concentration of 100 μM strongly inhibited both JMHD and TET1 dioxygenases, with effects even greater at 1 mM.  Comparing these concentrations to physiological concentrations reported during FQ therapy, serum concentrations of CIPRO are ~16 μM, but can approach 1-3 mM in the kidneys of treated patients.  Upon overdose, CIPRO concentrations in the urine are even higher.  Our choice of human embryonic kidney cells to study FQ effects reflects the high kidney exposure upon FQ treatment.   Indeed, acute renal failure is associated with high FQ concentration. . . . These results suggest, for the first time, that FQ treatment can cause unanticipated epigenetic effects.   This is the first study to show global epigenetic changes induced by FQ antibiotics.   Future studies will be needed to determine gene expression changes resulting from FQ treatment.”

Oxygen Sensing by HIF Hydroxylases   The transcription factor HIF (hypoxia-inducible factor) has a central role in oxygen homeostasis in animals ranging from nematode worms to man.  Recent studies have shown that this factor is regulated by an unprecedented signalling mechanism that involves post-translational hydroxylation.  This hydroxylation is catalysed by a set of non-haem, Fe2+-dependent enzymes that belong to the 2-oxoglutarate-dependent-oxygenase superfamily.  The absolute requirement of these enzymes for molecular oxygen has provided new insights into the way cells sense oxygen.”


V-ATPases (vacuolar H+-ATPase):   Target for Osteoporosis /Adverse Effects

Vacuolar-type H+ -ATPase (V-ATPase) is another enzyme that I would put right up there with the HIF1-related enzymes and proteins in terms of important additional unintentional targets to consider in FQT/FQAD.   Whereas HIF1a and dioxygenases are involved in oxygen homeostasis at a cellular level, V-ATPase is involved in acid-base, or pH homeostasis, at a cellular level.

It turns out that a couple of known FQs can inhibit V-ATPase activity.   The studies that are available on FQ -V-ATPase interactions are based on FQ potential to act as “anti-osteoporosis” drugs.   So here, I will focus on this one particular function of V-ATPase (bone break down and calcium homeostasis), since the research is available.  However, it’s important to remember that if FQs are targeting V-ATPase, much more will be affected than “just a little bone”.

V-ATPase is one of the most fundamental enzymes in nature, and appears to have remarkably diverse functions within our cells.   The pH of intracellular compartments in our cells is a carefully controlled parameter that affects many cellular processes, including intracellular membrane transport, prohormone processing and transport of neurotransmitters, as well as the entry of many viruses into cells.   For my purposes here, I’m going to focus on their role in bone resorption (bone breakdown).  Cellular pH regulators such as V-ATPase are potentially promising molecular targets for a number of conditions, including, of course, cancer.   For links and abstracts on V-ATPase, see  “References 14 ” .

Bone quality is maintained by a balance between bone formation, and bone breakdown. Cells called “osteoblasts” make bone, and cells called “osteoclasts” break down bone.   One of the times osteoclasts might be more active, is if we are low on calcium in our blood.   If we experience low calcium, our bodies will pull that calcium from our bones.   Mechanisms exist to activate osteoclasts to break down bone in order to release calcium.    While V-ATPase exists in all of our nucleated cells at a basal level, an unusual feature of osteoclasts is that V-ATPase is much higher in these cells.   This is because V-ATPase is required to help break down the bone and release calcium into the blood stream.

Hyper and Hypo Calcemia is serious business.  There is a long list of symptoms for both, many of which read a lot like what many FQT/FQAD victims experience.   For people who have read other parts of this website, you may remember that an entire endocrine system is dedicated to calcium homeostasis in the form of the parathyroid system, and that I recommend all FQT/FQAD victims regularly test for parathyroid-related parameters.   This is because I think “calcium homeostasis disruption” is also huge in FQT/FQAD victims, and although we can’t test for the numerous places this disruption can occur, the parathyroid system is one where we can.    I discuss some aspects of calcium disruption in “Additional Mechanisms to Consider” (scroll down to “The Parathyroid Glands and Calcium Homeostasis”), and how to test for Parathyroid-related parameters in “Thyroid and Parathyroid Related Testing.”  This by no means covers all the areas where “calcium homeostasis disruption” can occur.  Indeed, there are a huge number of ways intracellular calcium homeostasis disruption can occur that we can’t test for.  One of those mechanisms within this very long list includes V-ATPase activity.

When might a person need more V-ATPase activity to break down bone?   When they are low on calcium.   When might a person be low on calcium?   One reason might be, if they’re not getting enough calcium in their diet, or if they can’t absorb it well from the diet.    Another reason might be if too much calcium is being excreted, such as what might occur in late stage kidney disease.   And yet another reason might be if calcium is “bound up” and unavailable for use, or chelated and pulled out of cells and tissues and circulation – such as what might occur with the FQ antibiotics.    In these scenarios, mechanisms exist to try and maintain serum calcium levels by pulling calcium from the bones if necessary.    And this requires functional V-ATPase activity for the osteoclasts to do this job.

I was taking 600 mg Calcium supplements twice a day at the time I was prescribed Cipro for my UTI.   Since the package instructions warned not to take calcium supplements within several hours of taking the Cipro, which I was also instructed to take twice a day, I decided to stop the calcium supplements while on the Cipro.   I didn’t think this would be a big deal, because there were plenty of days and times I had skipped or stopped the calcium supplementation before without any adverse effects.    After all, I was a healthy person, presumably with a healthy parathyroid axis, and all mechanisms in place to make sure my serum calcium levels stayed within normal limits, such as what had occurred during the first 50 years of my life without thinking about such things.   I also was continuing to eat food, which presumably was also supplying me with calcium.

In hindsight, me stopping this calcium supplementation was a really, really, really, stupid idea (well, taking the FQ in the first place was actually the dumbest idea of all, so for anyone reading this, don’t be as dumb as I was).   In my case, I suspect I was “overdosed” with the Cipro (see the “Overdose Hypothesis” way up this page), which meant it was probably not only chelating calcium in my body, but affecting multiple systems to counteract this as well.   This might have included my parathyroid system, so that it couldn’t respond fast enough to attempt to correct any calcium homeostasis issues I might have been experiencing.    I’ll never know, because I didn’t know to test my parathyroid parameters during the acute phase.    My serum calcium levels were normal several weeks post the FQ, but I would have liked to have seen my PTH at the time.   So while on the FQ:

1) I stopped supplemental calcium, which my parathyroid axis had become accustomed to,

2) the FQ was probably chelating calcium out of my cells, tissues, and circulation as well, and

3) It turns out FQ’s interact with V-ATPase, preventing osteoclasts from doing their job of breaking down bone to provide calcium to the circulation when needed.

A triple whammy for “acute” hypocalcemia if there ever was one.   I did have the “oral, perioral and acral paresthesias, tingling or ‘pins and needles’ sensation in and around the mouth and lips, and in the extremities of the hands and feet, which is often the earliest symptom of hypocalcaemia” (from Wiki) during my acute phase.   I still get a waxing and waning tingling around my mouth and lips, which I’m convinced is related to “localized cellular calcium homeostasis” issues despite normal serum levels of calcium, over six years later.

I am convinced that taking a balance of calcium and magnesium, as “Peggy” has done here, ASAP after experiencing symptoms, might have helped me.   And knowing what I know now, I would have added in a good multi-mineral supplement and some “Fulvic/Humic” as well.  However, at the time I was first hit, I tried taking only magnesium, because that’s been the big recommendation for these reactions since the Stahlmann studies came out.   This made things worse for me.   My recommendation now would be to test for all minerals and PTH-related parameters, and as long as serum calcium is not high, supplement with a balance (not excess of any one) of Ca, Mg, and other minerals (also rule out kidney disorders and ACH-related transmission issues  before taking an excess of magnesium).   I don’t know that this would have solved or “fixed” my FQT/FQAD, but I believe had I done this, it most certainly would have helped, and it would not have hurt.   If you’ve read the rest of this page, you can see that there are multiple areas of damage that can occur with FQT/FQAD, and we can’t always control or fix those.   Different people will be affected to different extents, probably based on different genetic and epigenetic vulnerabilities.   I’m sure some FQT/FQAD victims have tried balanced mineral supplementation and, like me, are still symptomatic.   In my case, I did resume calcium and magnesium supplements fairly quickly, but in hindsight, I would have “hit it a little harder” by taking more of both, much earlier than I did, and made sure to throw in more of the other minerals as well.    I’m on as much of an overall mineral supplementation program now that I can tolerate, and it has helped, but has definitely not solved my FQT/FQAD.

Interestingly, I’ve read some FQT/FQAD victims describe “crushing bone pain” as being a part of their acute symptoms.   On the other hand, some FQT/FQAD victims have literally had their teeth crumble and fall out, usually as a delayed symptom.   Calcium is a big part of bones and teeth, and calcium homeostasis issues, both in serum and certainly within cells and organelles, is complex and highly interrelated.   V-ATPase is only one of numerous mechanisms which exist affecting calcium homeostasis, but I wonder if there might be V-ATPase suppression during the acute phase, and a “rebound effect” as a delayed effect.    Tendon rupture, which often presents as a delayed effect, could occur due to bone resorption at the tendon insertion sites (and these tendon insertion sites are often focally painful, and where the ruptures occur).    Low calcium itself does not cause tendon rupture, and I have seen at least one study suggesting it is high PTH regardless of calcium levels that is responsible; here, a consideration would be delayed or rebound activation of V-ATPase.    This “rebound effect” could be a desperate attempt to get intracellular and/or mitochondrial calcium stores back up to homeostasis levels again for cell signaling purposes and all the other numerous functions  calcium ions are necessary for.   Keep in mind that FQs have excellent intracellular penetration, and therefore may be “binding up”, chelating, or otherwise leaving calcium ions inaccessible at a cellular level.   V-ATPases may also contribute to extracellular and intracellular collagen degradation in soft connective tissue as well (see References 14 ), thereby having a direct effect in tendons as well as on the bone around tendon insertion sites.   On the page “Teeth: Pain and Deterioration”, I discuss how severe tooth deterioration started about Month 8 post for me, when I took a sudden turn for the worse (I described this as a “flare”, but it is different than the “”PGL/Pheo type flaring” I discussed above on this webpage).    The “Month 8 Post downturn” is when my facial neuropathy (described in “Trigeminal and Geniculate Neuralgia-Like Symptoms”) started in earnest, with “numb and painful teeth”, along with severe dryness of eyes, mouth, etc.   The tooth pain was unusual in that biting down pressure wasn’t painful, but the slightest “side to side” pressure was, to the point that flossing was painful.    If I grabbed the tooth and tried to move it, it was like the bone around it was painful, and I remember being concerned that some of my teeth felt “loose”.    At the time, I thought this was due to the periodontal ligament being painful, and that’s certainly as good a hypothesis as any, given the extreme tendon pain I’ve felt.   The periodontal ligament is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits.   Here, from a “V-ATPase point of view”, I wonder if it was the alveolar bone being affected that might have been playing a role and causing pain.   This V-ATPase hypothesis could account for the “teeth falling out and crumbling” which some FQT/FQAD victims have experienced.   In my case, the severe tooth wear I experienced seemed to occur during a couple of particularly bad phases, and appeared to stabilize more as my hormonal status stabilized.   I’m thankful I haven’t lost any teeth yet (in terms of crumbling and falling out), although I think there is a much slower, but continued wear rate occurring.  The “periodontal ligament / alveolar bone” pain waxes and wanes along with my other symptoms, and hormonal status continues to play a large role.   The “periodontal ligament /alveolar bone” pain was also there during the acute phase of my reaction, when my tendon pain was at its peak.

Another potential implication to consider with increased V-ATPase activity is lead toxicity.   I’ll use my own situation as an example, although it probably applies to most people my age.   I can still remember playing on that old third floor city tenement apartment building with huge flakes of peeling paint everywhere as a child.   Living in the city, lead was “everywhere” at that time anyway, even without ingesting it directly in paint.   So most people my age were exposed to levels of lead that today would be considered highly toxic (although back then, it wasn’t considered toxic, and in fact, the lead industry were trying to make it sound “healthy”, much like cigarette smoking).   Lead is stored in bone (which is why it’s so long lived in the body), but moves in and out of bone whenever bone is remodeled, and this includes when bone is broken down to access calcium.    When V-ATPase is more active, not only will more calcium be released, but more lead and other minerals and metals stored in bone will be released too.   With a delayed “rebound” effect of V-ATPase post FQ, I suppose there’s a possibility that for those with higher stores of lead in bone, “acute lead poisoning” could be occurring as well.   FQT/FQAD symptoms seem to have a lot in common with Lead Toxicity symptoms, and many studies suggest that some kind of “mineral disruption” is occurring in FQT/FQAD.   I would recommend FQT/FQAD victims run a lead blood test several times a year post FQ-reaction to check for this.   I wish I had known to do this during my acute stage for FQT/FQAD.   I think everyone in the population should be testing their blood levels for lead regularly anyway, as it’s so easy and inexpensive to do (see “Testing On Your Own — When the Docs Refuse“).   Lead Toxicity is one of those conditions where people will have variations in vulnerability due to individual genetics, healthy mineral status via a healthy diet and/or supplementation, and the amount of exposure in the environment.   Two out of those three can be changed and controlled (diet and environment), and the third (genetic susceptibility) could be identified via genetic testing if elevated serum lead levels are found.   An informative, as well as entertaining way to learn about the history of lead and the fight against lead toxicity can be seen in episode 7 of the Cosmos series: The Clean Room.

Similar mechanisms may be in play with fluoride and mercury, which also are stored in bone as well as other tissues (I pulled out a few of the more recent literature here, 1, 2, 3, 4, 5, 6, 7, 8).   I had a mouthful of mercury amalgam for thirty years before slowly replacing them all with composites.  I didn’t notice a difference in my symptoms after amalgam removal, and my serum and hair levels for mercury were always undetectable whenever I tested.  However, I didn’t run these tests during my acute stage post reaction, which is when V-ATPase activity might have been highest.  I also tested negative/undetectable for fluoride when I finally got around to testing for that about 1.5 years post.  As with lead and mercury, this is something I wish I would have tested during the acute stage (first six months) of my reaction.   Of course, fluoride is well known to affect the thyroid gland, so much so, that it was an initial treatment for hyperthyroidism.   As with lead toxicity, susceptibility to fluoride toxicity may have a genetic component to it (1), which may help explain why there seem to be different thresholds for tolerability and toxicity.

It’s important to remember that V-ATPase has a lot of important functions, not just the calcium-related one.  V-ATPases are found within the membranes of many organelles, such as endosomes, lysosomes, and secretory vesicles, where they play a variety of roles crucial for the function of these organelles.   Lysosomal storage diseases are a devastating group of disorders that result from defects in lysosomal function, and given V-ATPase roles with lysosomes, I wonder if some of the FQT/FQAD symptoms represent a “milder” form.    As I’ve suggested before in several places on this website, I suspect FQ’s may be damaging or affecting secretory cells in general, which would include endocrine and exocrine epithelial cells, and cells with well developed ER/Golgi apparatus.    FQ’s target rapidly proliferating cells — or possibly rapidly proliferating or transcriptionally active cellular products (ie, secretory products) via higher rates of topoisomerase activity for those products.    V-ATPases are heavily involved in hormone processing and neurotransmitter transport via secretory vesicles, and there’s no doubt I’ve got “homeostasis or regulatory” problems with my hormones and neurotransmitters going on.    V-ATPase is also involved in crucial cellular processes like morphogenesis, cell division, and migration via binding to actin, a protein that forms (together with myosin) the contractile filaments of muscle cells, which are important for muscle contraction.    From an FQ symptoms perspective, I wonder if the “burning/lactic acid” feeling in my muscles may also be related to this V-ATPase acid/base homeostasis issue, along with muscle weakness and “energy homeostasis issues”.   FQ-Induced V-ATPase damage or disruption could certainly account for or contribute to a wide variety of the symptoms I experience.

The “classic” time frame for tendon rupture with FQT is often 2-6 weeks post the antibiotic.   It’s well known that after suppression of the HPTaxis with thyroid medication, it takes a good 2 weeks, often longer, for serum levels to reach steady state levels when meds are discontinued (this is why clinicians typically wait 6-8 weeks after any change in thyroid dose, no matter how small, to re-test TSH). Tapering steroids (Pred) is often recommended for the same reasons with the HPA axis (to prevent a temporary, “iatrogenic Addisonian” state).   I wonder if a similar phenomenon might occur with the parathyroid axis. During FQ use, if intracellular calcium is falling, the “SOS” goes out, the PT axis tries to respond, but V-ATPase activity is blocked.   Once that FQ block is removed, PT axis continues to respond, V-ATPase levels are high and work to excess, even at the expense of ruptured tendons. Calcium homeostasis is pretty important and the PT axis needs to be responsive on a moment by moment basis. I don’t know if the fact I was supplying calcium helped to “suppress” the axis somewhat, such as what also occurs with the HPT/HPA axis.   It may take several weeks, or longer depending on how severe the calcium need is, before calcium homeostasis is returned to steady state and V-ATPase activity can return to normal levels in bone.  This is why I think taking a balance of calcium and magnesium, along with other minerals, is important during the acute stage and post antibiotic.    I never ruptured a tendon, but instead experienced severe systemic tendon pain, which I would say “peaked” at about the 3-6 week post mark, which is well within the “classic” time frame for tendon rupture and tendon pain.

Another additional interesting observation I made has to do with genetics.   In my own case, my parents are first cousins, so there is a small, but increased chance I am carrying rarer alleles that could make a difference.   The only genetic data I have on myself is from 23andMe.   I manually went through all the available data provided for the 23 genes in the V-ATPase family.   I didn’t have anyone else’s data for comparison, so all I could do was look for rarer alleles and genotype within my own data; I also did not exclude intron data.    Using NCBI dbSNP data for people of EUR origin, I found several fairly rare allele frequencies, with even lower genotype frequencies.   Interestingly, most were within the B1 and particularly, the B2 subunit – the subunit that interacts with FQs.  However, there were several others as well, in particular, the H subunit, which is considered a “regulatory” subunit.   As an example of what I was looking for, here is how I recorded information for one of the SNPs of the H subunit that I flagged:



rs16919513 54643399 A or G I am A / A

Ancestral = G, MAF A = 5%

EUR AF A = 0.8%, AFD EUR A/A = 0%

HM CEU A/A = 0.9%,


So according to these databases, not only is the minor A allele fairly rare, but the A/A genotype is very very rare for this SNP, and that’s what I have.   In contrast, I went through all the SNP’s for ATP-Synthase that I could find (I read that some of the subunits may be homologous in nature between V-ATPase and ATP synthase), and found only one rarer genotype of around 6% but with much higher allele frequencies (>20%).

Obviously, I’m working with pretty limited data, only my own data, and rarer alleles/genotypes don’t necessarily translate into problems (we all have plenty of them in our genome).    But I admit, I thought it was interesting that a couple of FQ’s have been shown to interact with the B subunit, and that was where most of my flagged data was.    I wonder if there might be an association.   It seems to me that if minute differences in FQ molecular structure can make such a difference between drug-protein interactions, then minute differences in our DNA/protein structure could equally do the same.   The FQ ADR’s also very much appear to be a class effect, and not limited to any one FQ derivative, so I suspect that at high enough doses (ie, if some people are unable to metabolize the drugs as effectively as others, which I also suspect in me), V-ATPases might be affected by more than just the few FQs studied.   The day before taking the antibiotic, I could get on my bicycle and ride 50 miles.   Five days later, I was completely disabled.   Many of my symptoms could be attributed to V-ATPase disruption, and here I’ve got several rarer alleles/genotypes within the V-ATPase gene, with most of them localized to the B2 subunit.

Of course, looking at the FQT/FQAD population genetics is the way to determine if V-ATPase genetics are playing a role in FQT/FQAD.    If a genetic signal is indeed found within the V-ATPase family, then testing both biological parents would help determine if this is a potential pre-existing vulnerability versus de novo mutations due to the FQ.   For people who have their 23andMe data, you can do a manual search such as I did (browse through your gene of interest, click on the rs number to go directly to the NCBI dbSNP page,  review data in the “Allele” box, and scroll down to see Population Diversity allele and genotype frequencies).   Of course, if you want to review a lot of genes, and want to save a lot of time and mind-numbing searching, use an automated software program such as Enlis, which appears to be reasonably priced.

V-ATPase is not the only ATPase out there; there are a whole bunch of them.    And in my opinion, I suspect any of them could be additional unintentional targets of FQs.  FQs seem to target enzymes involved with DNA, ATP, phosphorylation, functionally important tyrosines, and magnesium and other cations.  Human topoisomerase II enzymes have ATPase domains on them as well (see References 14 ).   As with V-ATPase, I flagged numerous rarer variation SNPs for my TOP2B gene – but only one for the TOP2A gene.  TOP2A promotes replication, transcription, chromosome structure and chromosome segregation, and is essential for cell proliferation and expressed mostly in dividing cells.   In contrast, TOP2B participates mainly in transcription and is expressed in both dividing and non-dividing cells   Per a couple of studies, TOP2B is “greatly expressed upon terminal differentiation of neuronal cells . . . and apparently genes involved in regulation of several ion channels and transporters, vesicle function, and cell calcium metabolism . . . suggesting that topoIIβ silencing can significantly alter the gene expression pattern of genes involved in a variety of biological processes and signal transduction pathways including transcription, translation, cell trafficking, vesicle function, transport, cell morphology, neuron guidance, growth, polarity, and axonal growth.”  In my own case, I wouldn’t be surprised if TOP2B was affected by the FQ I took as well.   For anyone using Enlis, I would check out whatever ATPase SNPs are provided by 23andMe.

I don’t know if this relevant to V-ATPase or not, but I’ll throw it out here just in case.    I have always been a slender person, with “fine” bones.   My wrists are so “thin” (small diameter), that I worried they would break when I tried to play volleyball when I was younger (which I loved).   I felt like I could literally feel my wrists bend and flex when that ball would slam into them when I tried to bump.   I’d wrap them up as much as I could, but eventually, I felt like I actually didn’t want to play volleyball anymore just for this reason alone.   I know it sounds strange, but I really was worried I could “break a wrist bone” due to playing volleyball.   I also have a mild to moderate scoliosis (only really visible on X-ray), which I assume is the most common form of “late-onset idiopathic scoliosis”.   I also assumed this at least partly contributed to the back pain I’ve experienced since my early twenties.  However, Scoliosis can be associated with a number of connective tissue and neuromuscular disorders as well.    Several years prior to being floxed, I also underwent a bone density scan under recommendation from a physician to have a baseline done before menopause.   At that time I was diagnosed as mildly osteopenic.   Some people who have osteopenia may not have bone loss.  They may just naturally have a lower bone density, especially thin people such as myself.   So I wasn’t particularly worried about this finding.   However, I did start calcium supplementation at that time as a result.   Again, I don’t know if these remarks are relevant to V-ATPase function or not, but here they are.

As with HIF1a, I think many, if not all, of my symptoms could be explained by a V-ATPase disruption as well.   Intracellular pH or acid-base homeostasis, is every bit as important as intracellular oxygen homeostasis; disruption or malfunction of either could be catastrophic.   Research is available implicating FQ-Induced disruption of both, even if only in the laboratory.   But these studies are an important start, and need to be considered and followed up on from an ADR and safety perspective.  Whether such studies will ever be done – or published — remains to be seen.

FQs have been shown to interact with the remarkably diverse enzyme called V-ATPase.    If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.    But for anything and everyone else — why take the risk?

Rational Identification of Enoxacin as a Novel V-ATPase-Directed Osteoclast Inhibitor.    “Here, we will focus on the direct interaction between V-ATPases and microfilaments that is mediated by the B2-subunit.   We will review efforts to understand the function of the microfilament binding site in the B2-subunit, and to develop small molecule inhibitors of the interaction as potential therapeutic agents using a knowledge-based approach.  A product of these studies was the identification of enoxacin, a novel inhibitor of osteoclast bone resorption.   Efforts are now underway to test the potential of enoxacin and other inhibitors of the B2-microfilament binding interaction for the treatment of bone disease in animal models.   Recently, it was reported that enoxacin is also a selective inhibitor of the virulence of Candida albicans, and of cancer growth and metastasis. The possible use of enoxacin and related molecules as anti-cancer chemotherapeutic agents emphasizes the need to fully understand the detailed mechanisms by which enoxacin affects cells.”

Identification of Enoxacin as an Inhibitor of Osteoclast Formation and Bone Resorption by Structure-Based Virtual Screening.    “An interaction between the B2 subunit of vacuolar H+-ATPase (V-ATPase) and microfilaments is required for osteoclast bone resorption. An atomic homology model of the actin binding site on B2 was generated and molecular docking simulations were performed. Enoxacin, a fluoroquinolone antibiotic, was identified and in vitro testing demonstrated that enoxacin blocked binding between purified B2 and microfilaments. Enoxacin dose dependently reduced the number of osteoclasts differentiating in mouse marrow cultures stimulated with 1,25-dihydroxyvitamin D3, as well as markers of osteoclast activity, and the number of resorption lacunae formed on bone slices. Enoxacin inhibited osteoclast formation at concentrations where osteoblast formation was not altered. In summary, enoxacin is a novel small molecule inhibitor of osteoclast bone resorption that acts by an unique mechanism and is therefore an attractive lead molecule for the development of a new class of antiosteoclastic agents . . . Bone quality is maintained by a balance between bone resorption by osteoclasts and bone formation by osteoblasts.1 Excess bone resorption can occur systemically, where it leads to osteoporosis,2 or locally, where it is associated with bone tumors,3,4 infections,5–7 and inflammatory responses.2,5,7 Although various agents are available for the treatment of excess osteoclast activity, none are ideal for the treatment of the associated pathologies. Osteoclasts are specialized cells of the hematopoietic lineage.8 Unusual features of osteoclasts include overexpression of vacuolar H+-ATPases (V-ATPasesa) and the transport of V-ATPases to the plasma membrane.9,10 While V-ATPases are expressed in all nucleated eukaryotic cells, where they are responsible for acidification of compartments of the endocytic pathway, V-ATPases are normally present at low levels and are forbidden to entry into the plasma membrane. The mechanisms underlying the overexpression of V-ATPases and their transport to the plasma membrane represent potential targets for therapeutic intervention that might be selective for osteoclast bone resorption . . . The fact that inhibition of the interaction between the B subunit and F-actin in biochemical assays and inhibition of osteoclast formation and bone resorption occurred in a similar concentration range is consistent with the results emanating from the same activity. However, during the course of the study, it was reported that enoxacin and some related fluoroquinolones stimulate RNA interference and enhance microRNA activity, also in a similar dose range.19 Micro-RNAs are a recently identified class of endogenously produced small RNAs that are thought to “fine tune” gene expression by binding to mRNAs and preventing their translation by sequestering them or triggering their degradation.20 Evidence was provided suggesting that enoxacin might interact with human immunodeficiency virus-1 transactivating response RNA-binding protein, a protein involved in loading the RNA-induced silencing complex. It seems unlikely (but not impossible) that stimulation of micro RNA activity could be the result of disruption of the interaction between V-ATPase and F-actin. Stimulation of micro RNA activity, regardless of the mechanism, could affect osteoclast differentiation . . . To explore this, we assayed several fluoroquinolones for their ability to affect the interaction between V-ATPase and F-actin in vitro and to inhibit osteoclast formation. These included norfloxacin, which was reported to stimulate microRNA activity and others (pefloxacin and levofloxacin) that did not.19,21 We found that only pefloxacin had a detectable effect on the interaction between B-subunit and F-actin. . . . Pefloxacin inhibited osteoclast formation, with an IC50 of about 50 μM compared with 10 μM for enoxacin (Figure 7B). The fact that norfloxacin, which also stimulates microRNA activity to similar levels as enoxacin,19,21 but does not block V-ATPase–F-actin interactions, had no effect on osteoclast differentiation suggests that the microRNA stimulation activity is not important in inhibiting osteoclast differentiation at the concentrations tested. This interpretation was further supported by the ability of pefloxacin, which does not stimulate microRNA activity,21 to block the V-ATPase–F-actin interactions and inhibit osteoclast formation. Taken together, these data are consistent with direct interference with the interaction between subunit B2 of V-ATPase and microfilaments being responsible for the inhibition in osteoclast formation. . . . The use of systemic enoxacin as an antibiotic has been linked to a number of adverse side effects. 22–24 These include phototoxicity, neurological problems, severe tendinitis, adverse immune activity, and renal failure due to distal renal tubular sensitivity. The capacity of enoxacin to block interactions between V-ATPase and microfilaments could represent an underlying mechanism for these adverse consequences. V-ATPases are key housekeeping enzymes, yet in certain specialized cell types, subpopulations of V-ATPases are vital for cell type specific functions. For example, in both osteoclasts and epithelial cells of the renal distal tubule, V-ATPases are expressed at high levels and inserted into the plasma membrane in order to pump protons from the cytosol to the extracellular environment.25 In neurons, V-ATPases are associated with loading neurotransmitters into vesicles and with the fusion of those vesicles with the presynaptic plasma membrane.26 Further studies will be required to examine the potential utility, as well as adverse effects, of enoxacin and related molecules.  In summary, we report the identification of enoxacin as an inhibitor of osteoclast formation and function by making use of a rational structure-based approach, utilizing molecular docking of a large chemical library in combination with biochemical and tissue culture assays. Our data suggest that enoxacin inhibits osteoclasts by a novel mechanism, blocking a binding interaction between the V-ATPase and microfilaments. V-ATPase activity is vital to osteoclast function, but because V-ATPase is expressed at low levels by all eukaryotic cells and performs housekeeping functions, efforts to use inhibitors of the proton pumping activity of V-ATPase to block bone resorption have not yet been successful. However, the interaction between V-ATPase and microfilaments has not been observed in most cell types studies but appears crucial for osteoclast function. We therefore reasoned that blocking the interaction might selectively inhibit osteoclastic bone resorption. Our data to date support this concept and encourage us to advance enoxacin as a lead molecule in the development of more potent and specific inhibitors of the interaction between V-ATPase B2-subunit and microfilaments as a new class of antiresorptive agents. We aim to identify safe and effective small molecules that represent a new class of antiosteoclastic agents that block bone resorption by two distinct strategies. First, we will analyze a series of 20 structural variants of enoxacin in structure–activity relationship studies. The most active compounds in this series will be elaborated (derivatized) and compared with the activity of parent compounds in blocking the B-subunit–F-actin binding interaction and in blocking osteoclast formation in vitro.  A separate strategy involves docking all FDA approved small molecules in the V-ATPase structural pocket comprised of Tyr68, Val89, Thr268, Ile269, Glu308, and Arg314. Additional FDA approved drugs (approved for other purposes) are expected to be identified. Because these compounds are approved for use, this strategy may rapidly result in evaluation in clinical trials.”

Enoxacin directly inhibits osteoclastogenesis without inducing apoptosis.   “Enoxacin has been identified as a small molecule inhibitor of binding between the B2-subunit of vacuolar H+-ATPase (V-ATPase) and microfilaments. It inhibits bone resorption by calcitriol-stimulated mouse marrow cultures. We hypothesized that enoxacin acts directly and specifically on osteoclasts by disrupting the interaction between plasma membrane-directed V-ATPases, which contain the osteoclast-selective a3-subunit of V-ATPase, and microfilaments . . . Our data show that enoxacin directly inhibits osteoclast formation without affecting cell viability by a novel mechanism that involves changes in posttranslational processing and trafficking of several proteins with known roles in osteoclast function. We propose that these effects are downstream to blocking the binding interaction between a3-containing V-ATPases and microfilaments . . . Enoxacin is a fluoroquinolone antibiotic that has been used extensively in humans for the treatment of urinary tract infections and gonorrhea with minimal side effects (2). Recently, unexpected properties of enoxacin have come to light. Our group, making use of a rational reverse chemical genetic strategy, identified enoxacin as an inhibitor of vacuolar H+-ATPase (V-ATPase)3-microfilament binding and of osteoclast formation and bone resorption in cell culture (1). Concurrently, others have identified enoxacin in screens for small molecule stimulators of RNA interference and microRNA activity (3, 4). Very recently enoxacin was reported to be a “cancer-specific” inhibitor that blocks the growth and metastases of human colorectal cancers in a mouse model (5). Because of the therapeutic potential of enoxacin, it is vital to understand the mechanisms by which it selectively affects osteoclasts. V-ATPases are essential “housekeeping” enzymes in all eukaryotic cells that are necessary for the acidification of compartments of the endocytic and phagocytic pathways (6, 7). Most cell types express only the low levels of V-ATPase required to carry out housekeeping functions, but some cell types also contain an additional subset of V-ATPases that plays a role in the unique functions of the cell. V-ATPases are composed of more than 10 subunits, and a number of these subunits have multiple isoforms. Housekeeping V-ATPases are composed of a specific subset of subunit isoforms, whereas non-housekeeping V-ATPases are marked by the inclusion of cell type-restricted isoforms of one or more of the subunits. These subpopulations are targeted and utilized differently than the housekeeping enzymes. Although it is well documented that particular isoforms of certain V-ATPase subunits are found in V-ATPases that are targeted to atypical cellular locations, the underlying mechanisms by which isoforms contribute to differential targeting and use of V-ATPases are not understood    ”

Bis-enoxacin inhibits bone resorption and orthodontic tooth movement.   “Enoxacin inhibits binding between the B-subunit of vacuolar H(+)-ATPase (V-ATPase) and microfilaments, and also between osteoclast formation and bone resorption in vitro. We hypothesized that a bisphosphonate derivative of enoxacin, bis-enoxacin (BE), which was previously studied as a bone-directed antibiotic, might have similar activities. BE shared a number of characteristics with enoxacin: It blocked binding between the recombinant B-subunit and microfilaments and inhibited osteoclastogenesis in cell culture with IC50s of about 10 µM in each case. BE did not alter the relative expression levels of various osteoclast-specific proteins. Even though tartrate-resistant acid phosphatase 5b was expressed, proteolytic activation of the latent pro-enzyme was inhibited. However, unlike enoxacin, BE stimulated caspase-3 activity. BE bound to bone slices and inhibited bone resorption by osteoclasts on BE-coated bone slices in cell culture. BE reduced the amount of orthodontic tooth movement achieved in rats after 28 days. Analysis of these data suggests that BE is a novel anti-resorptive molecule that is active both in vitro and in vivo and may have clinical uses.”

Ciprofloxacin is an inhibitor of the Mcm2-7 replicative helicase.    “Most currently available small molecule inhibitors of DNA replication lack enzymatic specificity, resulting in deleterious side effects during use in cancer chemotherapy and limited experimental usefulness as mechanistic tools to study DNA replication. Towards development of targeted replication inhibitors, we have focused on Mcm2-7 (minichromosome maintenance protein 2–7), a highly conserved helicase and key regulatory component of eukaryotic DNA replication. Unexpectedly we found that the fluoroquinolone antibiotic ciprofloxacin preferentially inhibits Mcm2-7. Ciprofloxacin blocks the DNA helicase activity of Mcm2-7 at concentrations that have little effect on other tested helicases and prevents the proliferation of both yeast and human cells at concentrations similar to those that inhibit DNA unwinding. Moreover, a previously characterized mcm mutant (mcm4chaos3) exhibits increased ciprofloxacin resistance. To identify more potent Mcm2-7 inhibitors, we screened molecules that are structurally related to ciprofloxacin and identified several that compromise the Mcm2-7 helicase activity at lower concentrations. Our results indicate that ciprofloxacin targets Mcm2-7 in vitro, and support the feasibility of developing specific quinolone-based inhibitors of Mcm2-7 for therapeutic and experimental applications. . . . One potential therapeutic target is the Mcm2-7 (minichromosome maintenance protein 2–7) eukaryotic replicative helicase, a molecular motor that unwinds duplex DNA to generate ssDNA templates for replication. Unlike other replicative helicases, the toroidal Mcm2-7 complex is formed from six distinct and essential subunits, numbered Mcm2 through Mcm7 [5]. Each subunit is an AAA+ ATPase. . . Following examination of amino acid modifiers and small molecule ATPase inhibitors [4,10,11], we found that the commercially available fluoroquinolone antibiotic ciprofloxacin preferentially inhibits the in vitro helicase activity of the Saccharomyces cerevisiae Mcm2-7 complex. Ciprofloxacin also appears to target Mcm2-7 in cell culture, as it blocks proliferation of both yeast and human cells at concentrations that inhibit the purified enzyme, and a previously studied cancer-causing mutation in Mcm4 confers ciprofloxacin resistance [15]. Additional inhibitors of greater potency were identified among compounds structurally related to ciprofloxacin. Several of these agents exhibited increased selectivity towards Mcm2-7, whereas others had varying specificities against a range of unrelated helicases. These data suggest that (fluoro)quinolone-based compounds may provide a general scaffold for future development of helicase inhibitors with targeted specificity . . . We reasoned that other (fluoro)quinolone derivatives might show enhanced Mcm2-7 specificity at potentially lower inhibitor concentrations. As the fluoroquinolones are used as antibiotics (reviewed in [24]), prior drug discovery efforts have resulted in the synthesis of chemically diverse libraries modeled on key elements found in the basic fluoroquinolone scaffold. Therefore we investigated a 144-compound chemical library that contained either (fluoro)quinolone derivatives or molecules with various substructures found in ciprofloxacin and other marketed quinolones . . . We provide evidence that ciprofloxacin (and to a lesser extent compound 271327) inhibits the activity of the budding yeast Mcm2-7 helicase both biochemically and in cell culture. Although our experiments largely focus on yeast, we also demonstrated that ciprofloxacin inhibits the viability of human cells at roughly similar concentrations. As fluoroquinolones have been extensively used in human medicine and theirpharmacological properties are established [24], the fluoroquinolone scaffold might well serve as a useful platform in the development of Mcm2-7 inhibitors with enhanced therapeutic potential. Although inhibition of Mcm2-7 occurs at ciprofloxacin concentrations higher than its normal therapeutic range (also see below), our results suggest that some of the side effects seen with this and other fluoroquinolones may be because of inhibition of DNA replication. . . . Both our in vitro and cell-based studies strongly support Mcm2-7 as a new eukaryotic target for fluoroquinolones. Our finding that the Mcm mcm4chaos3 mutant has significantly increased ciprofloxacin resistance provides evidence that at least part of fluoroquinolone cytotoxicity is likely due to defects in DNA replication. . . . Our results suggest that most of the studied inhibitors likely interfere with the ATPase active sites of the helicases . . . the discovery that fluoroquinolones can inhibit the eukaryotic helicase may explain some of the cytotoxic effects observed with ciprofloxacin and other fluoroquinolones [40]. Our finding that the mcm4chaos3 allele confers resistance to ciprofloxacin supports our hypothesis that the Mcm2-7 complex is a ciprofloxacin target in cells and suggests that it could also be contributing to the deleterious side effects seen with this class of compounds”.


Mitochondria:   Unintentional Target / Adverse Effects

Mitochondrial Toxicity is currently high on the list as a contender for FQT/FQAD, and there are plenty of references already which would support this hypothesis.   Although present-day mitochondria do synthesize a few of their own proteins, the vast majority of the proteins they require are now encoded in the nuclear genome.   Because of the highly symbiotic nature of mitochondria with their host cells, I find it hard to separate out “mitochondrial toxicity” from overall “cellular toxicity”.   Mitochondria are highly dependent on many metabolites from the host cell, so if there’s a problem with the host cell providing these metabolites, mitochondria will suffer too.    And we’ve seen a pretty good list of unintentional targets of FQs to the host cell so far, all of which would negatively affect mitochondria.   On the other hand, the host cell can longer survive or function well without viable and well functioning mitochondria, so the reverse is true as well.   Mitochondria have plenty of their own dehydrogenases, oxidases, peroxidases, etc., and these appear to also be “on the list” of unintentional targets of FQ’s.   In this way, mitochondria could take “direct hits” from FQs as well.   In addition, if some of the present day mitochondrial enzymes, receptors, or transporters resemble their bacterial homologues “a little too much”, especially in those of us with FQT/FQAD, this could potentially be another reason that those of us with FQT/FQAD were hit harder than the rest of the population who appear to take these drugs safely.   Lastly, the mitochondrial genome may be particularly prone to DNA damage from chemotherapeutic drugs overall, and that includes FQs.   With the “Overdose Hypothesis”, anyone getting an unintentional “supra-therapeutic dose” or “overdose” of FQs might very well have their mitochondria take a pretty good hit during treatment, possibly to non-recoverable levels.    For example, here is a study showing that in patients who have been treated for cancer, there is an increased level of mitochondrial DNA damage:

Changes in the human mitochondrial genome after treatment of malignant disease.   “Mitochondrial DNA (mtDNA) is the only extrachromosomal DNA in human cells. The mitochondrial genome encodes essential information for the synthesis of the mitochondrial respiratory chain. Inherited defects of this genome are an important cause of human disease. In addition, the mitochondrial genome seems to be particularly prone to DNA damage and acquired mutations may have a role in ageing, cancer and neurodegeneration. We wished to determine if radiotherapy and chemotherapy used in the treatment of cancer could induce changes in the mitochondrial genome. Such changes would be an important genetic marker of DNA damage and may explain some of the adverse effects of treatment. We studied samples from patients who had received radiotherapy and chemotherapy for point mutations within the mtDNA control region, and for large-scale deletions. In blood samples from patients, we found a significantly increased number of point mutations compared to the control subjects. In muscle biopsies from 7 of 8 patients whom had received whole body irradiation as well as chemotherapy, the level of a specific mtDNA deletion was significantly greater than in control subjects. Our studies have shown that in patients who have been treated for cancer there is an increased level of mtDNA damage.”

I didn’t spend a lot of time on FQ-Induced mitochondrial toxicity in this website because it is covered so well in other websites.   However, I firmly believe that I have some “FQ-Induced mitochondrial toxicity” in that I feel I’m either missing some pretty important enzyme functions, or my mitochondrial levels overall are continuing to decline.   I did spend time trying all the “mitochondrial supplements” out there, including TCA intermediates and amino acid precursors, alone and in combination, with and without vitamin and mineral cofactors, and reached a “block” with all of them.   Some of them I had an immediate and dramatic reaction, such as I described above with aKG.   Others helped initially for a day or two, before symptoms started as a “build up”, or “inability to further metabolize the supplement” occurred.   Here is the type of study I wish could have been done on me in Year 6 and 7 post as my condition continued to deteriorate:

A mitochondrial cytochrome b mutation causing severe respiratory chain enzyme deficiency in humans and yeast.   “Whereas the majority of disease-related mitochondrial DNA mutations exhibit significant biochemical and clinical heterogeneity, mutations within the mitochondrially encoded human cytochrome b gene (MTCYB) are almost exclusively associated with isolated complex III deficiency in muscle and a clinical presentation involving exercise intolerance. Recent studies have shown that a small number of MTCYB mutations are associated with a combined enzyme complex defect involving both complexes I and III, on account of the fact that an absence of assembled complex III results in a dramatic loss of complex I, confirming a structural dependence between these two complexes. We present the biochemical and molecular genetic studies of a patient with both muscle and brain involvement and a severe reduction in the activities of both complexes I and III in skeletal muscle due to a novel mutation in the MTCYB gene that predicts the substitution (Arg318Pro) of a highly conserved amino acid. Consistent with the dramatic biochemical defect, Western blotting and BN-PAGE experiments demonstrated loss of assembled complex I and III subunits. Biochemical studies of the equivalent amino-acid substitution (Lys319Pro) in the yeast enzyme showed a loss of enzyme activity and decrease in the steady-state level of bc1 complex in the mutant confirming pathogenicity.”

This is the type of study I would like to see done on the FQT/FQAD population in general.   In Year 6 and 7, I developed extreme progressive muscle weakness, with a “lactic acid” type burning building up with any use.  This was most evident in my thigh muscles, and by the end, I felt like I was operating on less than 5% of whatever my original healthy thigh muscle strength would have been.   I could no longer walk or even stand for more than a minute or two, as a result of this.    It also simply felt like I was no longer running on “aerobic respiration”.   The “burning” feeling would occur with the slightest use, and with every thyroid hormone dose (which I was taking twice a day).   In other words, any increase in metabolism was starting to result in this burning neuropathy throughout my skeletal muscles.   My thigh muscles were the worst, but these symptoms were progressing to my arms, diaphragm, and all other skeletal muscles as well.   (As an update:  I did actually manage to improve the above symptoms, in particular the neuropathy, by increasing my overall mineral supplementation and Vitamin D again.   However, any improvement I made appears to have reached a plateau for the past several months, and I can’t seem to “push it” any further with the supplements).

For a variety of reasons, I was looking closely at the ɑKG – succinate area of the TCA/ETC, with corresponding enzymes and cofactors, as being a problem for me since being floxed.   I ended up thinking a lot about cytochrome bc, oxidase, or peroxidase, which is what led me to the above study.  However, I use the above study as an example of what could be done for all the mitochondrial genes – not just the topoisomerases or cytochrome b.   As stated from this study:  “On account of the clinical and genetic heterogeneity exhibited by mitochondrial disorders, the investigation and diagnosis of patients suspected of a respiratory chain abnormality remain a considerable challenge.  Although some patients present with a well-recognized clinical phenotype due to a specific mutation (in either the mitochondrial or nuclear genome), for many who exhibit clinical features consistent with a mitochondrial aetiology, a definitive diagnosis requires a combination of techniques including histochemistry, biochemical assessment of respiratory chain function and molecular genetic studies.  In the case of genetic studies, this may include sequencing of the entire mitochondrial genome to screen for rare or novel causative mutations.”

Inherited mitochondrial genetic defects are devastating conditions for the people who suffer from them.   Children who inherited these defects had no choice.   But as adults, we do have a choice to stay away from “mitotoxic” drugs, once we know about them.    And the fluoroquinolone antibiotics are in this category.   And once you know and understand this, why in the world would you want to take a drug, such as an FQ, that can cause acquired mitochondrial genetic defects, leaving you debilitated for life?   Why in the world would the FDA allow these mitotoxic drugs to be passed out like candy to the unsuspecting public?

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.   But for anything and everyone else — why take the risk?

For more information about FQ-Induced Mitochondrial Toxicity, see the following website links:

MyQuinStory Website:   Articles and FDA updates about FQ-Induced mitochondrial toxicity.

Floxie Hope Website:   First 14 links are about FQ-Induced mitochondrial toxicity.

Mitochondrial Damage and Depletion:   Here, I discuss mitochondrial issues in the context of thyroid related issues.


Adverse effects of antimicrobials via predictable or idiosyncratic inhibition of host mitochondrial components.   “This minireview explores mitochondria as a site for antibiotic-host interactions that lead to pathophysiologic responses manifested as nonantibacterial side effects. Mitochondrion-based side effects are possibly related to the notion that these organelles are archaic bacterial ancestors or commandeered remnants that have co-evolved in eukaryotic cells; thus, this minireview focuses on mitochondrial damage that may be analogous to the antibacterial effects of the drugs . . . Chloramphenicol and fluoroquinolones target bacterial ribosomes and gyrases/topoisomerases, respectively, both of which are present in mitochondria. However, the side effects of chloramphenicol and the fluoroquinolones appear to be based on idiosyncratic damage to host mitochondria. Nonetheless, it appears that mitochondrion-associated side effects are a potential aspect of antibiotics whose targets are shared by prokaryotes and mitochondria-an important consideration for future drug design.”

Role of mitochondria in ciprofloxacin induced apoptosis in bladder cancer cells.   “The disruption of calcium homeostasis, mitochondrial swelling and redistribution of Bax to the mitochondrial membrane are key events in the initiation of apoptotic processes in ciprofloxacin treated bladder cancer cells.”

Calcium signals are affected by ciprofloxacin as a consequence of reduction of mitochondrial DNA content in Jurkat cells.   “The effects of ciprofloxacin on mitochondrial DNA (mtDNA) content, oxygen consumption, mitochondrial membrane potential, cellular ATP formation, and capacitative Ca(2+) entry into Jurkat cells were investigated. In cells incubated for several days with 25 mug/ml ciprofloxacin, a 60% reduction of mtDNA content, inhibition of the respiratory chain, and a significant decrease in mitochondrial membrane potential were observed. These changes led to a decrease in the calcium buffering capacity of mitochondria which, in turn, resulted in a gradual inhibition of the capacitative Ca(2+) entry. On days 4, 7, and 11 of incubation with ciprofloxacin, the initial rates of Ca(2+) entry were reduced by 33%, 50%, and 50%, respectively. Ciprofloxacin caused a transient decrease in the cellular capability for ATP formation. In cells incubated for 15 min with glucose, pyruvate, and glutamine as exogenous fuel, ciprofloxacin reduced ATP content by 16% and 35% on days 4 and 7, respectively, of incubation with the drug. However, on day 11 of incubation with ciprofloxacin, a recovery of cellular ATP formation was observed. In conclusion, long-term exposure of Jurkat cells to ciprofloxacin at a concentration of 25 mug/ml seriously affects cellular energy metabolism and calcium homeostasis. . . . Mitochondria play a crucial role in ATP synthesis in all aerobic animal cells. ATP produced by oxidative phosphorylation covers nearly 90% of cellular energy demands. Apart from ATP synthesis, mitochondria are the site of numerous metabolic processes and are involved in the regulation of cellular calcium signals. To fulfill these functions, mitochondria must generate a high electrochemical proton gradient (ΔΨ) across the inner membrane. Their de-energization due to inhibition of the respiratory chain or to uncoupling of oxidative phosphorylation may result in cellular energy deficiency and impairment of ΔΨ-dependent processes, among them intracellular calcium signaling (11, 15, 26, 27). In metazoa mitochondrial DNA (mtDNA) typically encodes 13 proteins involved in oxidative phosphorylation; two of them are elements of the Fo subunit of mitochondrial ATPase, while 11 proteins are components of the respiratory chain complexes I, III, and IV. In addition, mtDNA contains 22 genes encoding tRNAs and two genes for rRNA. Therefore, perturbations in mtDNA content and/or processing may cause severe impairments in the cellular energy metabolism. Ciprofloxacin is a 4-fluoroquinolone antibiotic commonly used in therapy of many microbial infections. Its antibacterial activity is based on the inhibition of the bacterial enzyme DNA gyrase. Unfortunately, this compound also inhibits mammalian topoisomerase II, especially its mitochondrial isoform. This side effect results in improper mtDNA replication and therefore causes mtDNA fragmentation and a gradual decrease in mtDNA content (4, 14). A prolonged exposure of murine leukemia cells to ciprofloxacin applied at concentrations ranging from 20 to 80 μg/ml results in a gradual depletion of mtDNA with a concomitant reduction of the respiration rate and stimulation of glycolysis (14). Disturbance of the mitochondrial energy metabolism has been proposed to explain the cytotoxic effect of ciprofloxacin. The sensitivities of various cell lines to ciprofloxacin may differ significantly (13, 14). Some of them, for example, bladder cancer cells, exposed to low concentrations of this compound may undergo irreversible changes leading to apoptotic death (2, 3). Ciprofloxacin applied at a concentration of 80 μg/ml was found to both stimulate and inhibit transcription of many genes in human lymphocytes (6). Capacitative calcium entry, the most common pathway of Ca2+ influx in electrically nonexcitable cells, is preceded by calcium release from the lumen of the endoplasmic reticulum (ER). In other words, opening of the plasma membrane Ca2+ channels, the so-called store-operated calcium channels (SOCs), depends on the filling state of intracellular calcium stores (17, 19, 20). In many electrically nonexcitable cell types, including Jurkat cells, energized mitochondria are necessary for intensive calcium influx through SOCs to occur. It is well established that respiring, well-coupled mitochondria buffer the excess of calcium accumulated in the vicinity of calcium channels and thereby limit local Ca2+ concentration. This reduces the feedback inhibition of calcium channels and promotes their open state (7, 8, 11, 15, 16). The main purpose of this study was to correlate the effects of long-term exposure to a relatively low concentration (25 μg/ml) of ciprofloxacin on the mtDNA content and mitochondrial energy state (expressed as the respiration rate and ΔΨ) with those on capacitative calcium influx and viability of human lymphoidal cells (Jurkat). We show that ciprofloxacin induces a decrease in both the mitochondrial respiration rate and ΔΨ in parallel with a reduction of the mtDNA content. More importantly, the changes in the mitochondrial energy metabolism correlate with decreased calcium entry into these cells. Because the capacitative mode of Ca2+ influx is the major route of calcium entry into lymphocytes, it seems possible that ciprofloxacin-evoked inhibition of cell proliferation may, at least partially, result from aberrant calcium signals. There is a growing body of evidence that ciprofloxacin, especially at higher concentrations, in the range from 50 μg/ml to 400 μg/ml, interferes with the cell cycle at the S/G2 checkpoint and commits cells to the apoptotic pathway. It also induces apoptosis in activated Jurkat cells (12). Recently, numerous reports have been published concerning the antitumor activity of ciprofloxacin based on stimulation of apoptosis in various malignant cells. This makes ciprofloxacin a candidate anticancer drug (3, 10).”

Delayed cytotoxicity and cleavage of mitochondrial DNA in ciprofloxacin-treated mammalian cells.     “We have previously shown that 4-quinolone drugs cause a selective loss of mitochondrial DNA (mtDNA) from mouse L1210 leukemia cells. The loss in mtDNA was associated with a delayed loss in mitochondrial function. Here, we report that the 4-quinolone drug ciprofloxacin is cytotoxic to a variety of cultured mammalian cell lines at concentrations that deplete cells of mtDNA . . . Resistance was not due to a decrease in cellular drug accumulation, suggesting that ciprofloxacin cytotoxicity is caused by the loss of mtDNA-encoded functions. Analysis of mtDNA from ciprofloxacin-treated cells revealed the presence of site-specific, double-stranded DNA breaks. Furthermore, exonuclease protection studies indicated that the 5′-, but not the 3′-, ends of the drug-induced DNA breaks were tightly associated with protein. These results suggest that ciprofloxacin may be causing cytotoxicity by interfering with a mitochondrial topoisomerase II-like activity, resulting in a loss of mtDNA.”

High-content screening for compounds that affect mtDNA-encoded protein levels in eukaryotic cells.   “The results confirmed effects of drugs known to reduce mtDNA-encoded protein levels and also revealed novel information showing that several fluoroquinolones impaired expression of mtDNA-encoded proteins.”

Role of mitochondria in ciprofloxacin-induced apoptosis in murine sperm cells.   “Ciprofloxacin (CPFX) has been reported to inhibit cell growth and induce apoptosis in certain eukaryotic cells . . . Effects of clinically reachable doses of CPFX on cultured murine sperm cells were investigated and revealed that it may cause sperm cell toxicity by induction of apoptosis through the mitochondrial pathway in the clinically reachable concentrations.”

In vitro study of cytotoxicity of quinolones on rabbit tenocytes.   “First, we examined their effects on cell viability, mitochondrial succinate dehydrogenase and global activity, mitochondrial activity using microtitration methods. Pefloxacin and norfloxacin were more cytotoxic than nalidixic acid according to IC50 values. These results confirm that mitochondria represent a biological target of fluoroquinolones.”

Literature Search Strategy for Mechanism of Action.” “Search Terms” include “mitochondria,” “mtDNA,” “oxidative stress,” and “apoptosis.” Literature was searched from January 1980 to December 2012. (FDA, 2013, page 6) Section 3.3.2 of this FDA document is titled, “Possible Mechanism of Action: Mitochondrial Toxicity,” and explains: “Fluoroquinolones have been found to affect mammalian topoisomerase II, especially in mitochondria. In vitro studies in drug-treated mammalian cells found that nalidixic acid and ciprofloxacin caused a loss of mitochondrial DNA (mtDNA), resulting in a decrease of mitochondrial respiration and an arrest in cell growth.” (FDA, 2013, pages 11-12) “Mitochondrial conditions that are due to an insufficiency of ATP, especially in organs that rely on mitochondria for their energy source, include developmental disorders of the brain, optic neuropathy, neuropathic pain, hearing loss, muscle weakness, cardiomyopathy, and lactic acidosis. Neurodegenerative diseases, like Parkinson’s, Alzheimer’s and amyotrophic lateral sclerosis (ALS) have been associated with the loss of neurons due to oxidative stress.” (FDA, 2013, page 12) . . . Section 8.6 of this FDA document is titled, “Possible Mechanism of Action: Mitochondrial Toxicity,” and explains: “In vitro studies in drug-treated mammalian cells found that nalidixic acid and ciprofloxacin caused a loss of mitochondrial DNA (mtDNA), resulting in a decrease of mitochondrial respiration and an arrest in cell growth. Further analysis found protein-linked double-stranded DNA breaks in the mtDNA from ciprofloxacin-treated cell, suggesting that ciprofloxacin was targeting topoisomerase II activity in the mitochondria.” (FDA, 2013, page 24)

Trovafloxacin, a fluoroquinolone antibiotic with hepatotoxic potential, causes mitochondrial peroxynitrite stress in a mouse model of underlying mitochondrial dysfunction.   “Trovafloxacin (TVX) is a fluoroquinolone antibiotic whose therapeutic use was severely restricted due to an unacceptable risk of idiosyncratic liver injury. Oxidative stress and mitochondrial injury have been implicated in fluoroquinolone toxicity, but the mechanisms underlying liver injury are poorly understood. Because TVX-induced hepatotoxicity cannot be modeled in normal healthy rodents, we asked whether an underlying genetic defect (heterozygous deficiency in mitochondrial superoxide dismutase, Sod2) might aggravate TVX-induced mitochondrial adverse effects . . . These data indicate that TVX enhances hepatic mitochondrial peroxynitrite stress in mice with underlying increased basal levels of superoxide, leading to the disruption of critical mitochondrial enzymes and gene regulation.”

Fluoroquinolone-related neuropsychiatric and mitochondrial toxicity: a collaborative investigation by scientists and members of a social network.   “New serious FQ-associated safety concerns have been identified through novel collaborations between FQ-treated persons who have developed long-term neuropsychiatric (NP) toxicity, pharmacovigilance experts, and basic scientists . . . For the survey, 93 of 94 respondents reported FQ-associated events including anxiety, depression, insomnia, panic attacks, clouded thinking, depersonalization, suicidal thoughts, psychosis, nightmares, and impaired memory beginning within days of FQ initiation or days to months of FQ discontinuation. The FDA Adverse Event Reporting System (FAERS) included 210,705 adverse events and 2,991 fatalities for FQs. Levofloxacin and ciprofloxacin toxicities were neurologic (30% and 26%, respectively), tendon damage (8% and 6%), and psychiatric (10% and 2%). In 2013, an FDA safety review reported that FQs affect mammalian topoisomerase II, especially in mitochondria.”

Repositioning of antibiotic levofloxacin as a mitochondrial biogenesis inhibitor to target breast cancer.   “Targeting mitochondrial biogenesis has become a potential therapeutic strategy in cancer due to their unique metabolic dependencies. In this study, we show that levofloxacin, a FDA-approved antibiotic, is an attractive candidate for breast cancer treatment . . . Importantly, levofloxacin inhibits mitochondrial biogenesis as shown by the decreased level of mitochondrial respiration, membrane potential and ATP. In addition, the anti-proliferative and pro-apoptotic effects of levofloxacin are reversed by acetyl-L-Carnitine (ALCAR, a mitochondrial fuel), confirming that levofloxacin’s action in breast cancer cells is through inhibition of mitochondrial biogenesis. A consequence of mitochondrial biogenesis inhibition by levofloxacin in breast cancer cells is the deactivation of PI3K/Akt/mTOR and MAPK/ERK pathways.”

Effect of fluoroquinolones on mitochondrial function in pancreatic beta cells.    “Hyper- and hypoglycaemias are known side effects of fluoroquinolone antibiotics, resulting in a number of fatalities.   Fluoroquinolone-induced hypoglycaemias are due to stimulated insulin release by the inhibition of the KATP channel activity of the beta cell . . . In conclusion, fluoroquinolones affect the function of the mitochondria in pancreatic beta cells which may diminish the insulinotropic effect of KATP channel closure and contribute to the hyperglycaemic episodes.”

The effect of moxifloxacin on apoptosis of airway smooth muscle cells and mitochondria membrane potential.   “To observe the effects of moxifloxacin at various concentrations on the expression of Caspase-3, the alteration of mitochondria membrane potential (ΔΨm) and the apoptosis of airway smooth muscle cells (ASMCs), and to explore the possible mechanisms . . . Moxifloxacin was shown to promote ASMC apoptosis by altering ΔΨm.”

Mitochondrial reactive oxygen species control T cell activation by regulating IL-2 and IL-4 expression: mechanism of ciprofloxacin-mediated immunosuppression.    “Ciprofloxacin, as well as other members of the fluoroquinolone group of antibiotics, is characterized by immunomodulatory properties of an unknown mechanism (10). The effects of ciprofloxacin on T cell activation-induced gene expression remain vague. Numerous conflicting reports stated that ciprofloxacin activates or inhibits T cell activation-induced gene expression (e.g., for IFN-γ, TNF-α, IL-2, and IL-4) (11–14). Interestingly, as an inhibitor of bacterial topoisomerase II and an inducer of DNA double-strand breaks, ciprofloxacin was also shown to deplete the mitochondrial DNA (mtDNA) content, thus leading to mitochondrial dysfunction and retarded cellular growth (15–17).   In this article, we show that prolonged ciprofloxacin treatment of preactivated human T cells leads to a loss of mtDNA content. This was accompanied by impaired activity of the mtDNA-encoded mitochondrial enzymes, such as complex I, whereas the activities of the nuclear-encoded mitochondrial enzymes, complex II (succinate dehydrogenase) and citrate synthase, were unaffected. In addition, prolonged ciprofloxacin treatment results in a dose-dependent inhibition of the T cell activation-induced oxidative signal, as well as IL-2 and IL-4 gene expression. Furthermore, by using various experimental models, such as ethidium bromide (EB)-induced mtDNA depletion, inhibition of complex I, or small interfering RNA (siRNA)-mediated knockdown of the complex I chaperone NDUFAF1, we demonstrate that TCR-triggered ROS generation by the mitochondrial complex I is indispensable for T cell activation-induced IL-2 and -4 expression in resting and preactivated human T cells. . . .  Moreover, our results postulate a detailed analysis of the T cell activation phenotype in patients with mitochondrial complex I dysfunctions or mtDNA deletions. . . . The immunomodulatory properties of ciprofloxacin and other drugs of the fluoroquinolone group are well documented (10). Most of the in vitro studies showed stimulatory effects of immediate or short-term (up to 72 h) ciprofloxacin treatment on basal gene expression in peripheral mitogen-preactivated human T cells (11, 12, 24). However, several in vitro and in vivo studies suggested that ciprofloxacin has inhibitory properties toward T cell activation (10, 13, 14, 28). In addition, in vitro experiments demonstrated that prolonged ciprofloxacin treatment retards cellular growth (25). This cytostatic effect is mediated by inhibition of the putative mitochondrial topoisomerase II in proliferating cells, resulting in a gradual mtDNA loss and energy shortage (16, 25). Our previous work showed that the mitochondria-generated oxidative signal, in the form of H2O2, is indispensable for T cell activation-induced expression of CD95L, a crucial AICD mediator (9). Thus, it is important to clarify whether ciprofloxacin-induced mitochondrial dysfunction could account for differential effects of ciprofloxacin on activation-induced gene expression in T cells. Supporting previously published data, we show that long-term ciprofloxacin treatment (7 d) of mitogen-activated proliferating peripheral human T lymphocytes led to a decreased mtDNA content (Fig. 1E). Interestingly, prolonged ciprofloxacin treatment clearly blocked TCR-induced expression of IL-2 and IL-4 genes (Fig. 1B). Of note, ciprofloxacin moderately increased basal IL-2 and -4 expression (Fig. 1A), which corresponds with previously reported data (11, 12, 24). Parallel to the inhibitory effect on activation-induced IL-2 and IL-4 gene expression, ciprofloxacin reduced TCR-triggered ROS levels in a dose-dependent fashion (Fig. 2C). Experimental results obtained using Jurkat T cells transiently depleted of mtDNA (ps-ρ0 phenotype) clearly attributed mtDNA loss to observed effects of ciprofloxacin treatment (Fig. 2D–F). The activation-induced IL-2 and -4 expression levels, as well as the level of activation-induced ROS, were lower in ps-ρ0 Jurkat T cells compared with the parental cell line. Mitochondrial ETC complex I functions as a generator of the activation-induced oxidative signal in preactivated human T cells (“day 6” T cells) (9). As a result of mtDNA depletion (Fig. 1E), long-term ciprofloxacin treatment reduced the activity of mtDNA-encoded complex I (Fig. 2A). Therefore, we investigated whether mitochondrial complex I-generated ROS influences IL-2 and -4 expression in preactivated human T cells. . . .. In conclusion, these findings open new possibilities for use of this drug [Ciprofloxacin]. However, the ability of ciprofloxacin to induce delayed-type hypersensitivity via direct TCR triggering (51) may pose difficulties to the topical application of ciprofloxacin to alleviate skin inflammation.

The mitochondria targeted antioxidant MitoQ protects against fluoroquinolone-induced oxidative stress and mitochondrial membrane damage in human Achilles tendon cells.   “Tendinitis and tendon rupture during treatment with fluoroquinolone antibiotics is thought to be mediated via oxidative stress. This study investigated whether ciprofloxacin and moxifloxacin cause oxidative stress and mitochondrial damage in cultured normal human Achilles’ tendon cells and whether an antioxidant targeted to mitochondria (MitoQ) would protect against such damage better than a non-mitochondria targeted antioxidant. Human tendon cells from normal Achilles’ tendons were exposed to 0-0.3 mM antibiotic for 24 h and 7 days in the presence of 1 microM MitoQ or an untargeted form, idebenone. Both moxifloxacin and ciprofloxacin resulted in up to a 3-fold increase in the rate of oxidation of dichlorodihydrofluorescein, a marker of general oxidative stress in tenocytes (p<0.0001) and loss of mitochondrial membrane permeability (p<0.001). In cells treated with MitoQ the oxidative stress was less and mitochondrial membrane potential was maintained. Mitochondrial damage to tenocytes during fluoroquinolone treatment may be involved in tendinitis and tendon rupture.”

The inhibition of gluconeogenesis by gatifloxacin may contribute to its hypoglycaemic action.   “The action of gatifloxacin, the broad-spectrum fluoroquinolone antibiotic commonly used in the therapy of various bacterial infections, was investigated in isolated rabbit hepatocytes and kidney-cortex tubules by measuring the activity of gluconeogenesis, a process that maintains whole body glucose homeostasis . . . At concentrations between 25 and 200 microM the drug decreased mitochondrial oxygen consumption by 20-45% with pyruvate + malate and ADP. As in the case of alpha-cyano-4-hydroxycinnamate, a well-established inhibitor of the mitochondrial pyruvate transporter, it diminished pyruvate uptake by both renal and hepatic mitochondria. The inhibitory action of gatifloxacin was less pronounced in hepatocytes where reduction in pyruvate-dependent glucose formation and mitochondrial respiration was by no more than 25%. The antibiotic did not influence mitochondrial oxygen consumption with glutamate + malate in either kidney-cortex or liver mitochondria. A differential substrate dependence of gatifloxacin action on gluconeogenesis and mitochondrial respiration combined with a decrease in pyruvate uptake by mitochondria suggest that the inhibitory action of this drug on gluconeogenesis might result from its impairment of pyruvate transport into mitochondria.”

Ofloxacin induces apoptosis in microencapsulated juvenile rabbit chondrocytes by caspase-8-dependent mitochondrial pathway.    “Quinolones (QNs)-induced arthropathy is an important toxic effect in immature animals leading to restriction of their therapeutic use in pediatrics. However, the exact mechanism still remains unclear. Recently, we have demonstrated that ofloxacin, a typical QN, induces apoptosis of alginate microencapsulated juvenile rabbit joint chondrocytes by disturbing the beta 1 integrin functions and inactivating the ERK/MAPK signaling pathway. In this study, we extend our initial observations to further elucidate the mechanism(s) of ofloxacin-induced apoptosis by utilizing specific caspase inhibitors. . . . Ofloxacin also stimulated a concentration-dependent translocation of cytochrome c from mitochondria into the cytosol and a decrease of mitochondrial transmembrane potential, which was completely inhibited by zIETD-fmk. In addition, ofloxacin was found to increase the level of Bax, tBid, p53 in a concentration- and time-dependent manner. Taken together, the current results indicate that the caspase-8-dependent mitochondrial pathway is primarily involved in the ofloxacin-induced apoptosis of microencapsulated juvenile rabbit joint chondrocytes.”

Microarray analysis in human hepatocytes suggests a mechanism for hepatotoxicity induced by trovafloxacin.   “Idiosyncratic drug toxicity, defined as toxicity that is dose independent, host dependent, and usually cannot be predicted during preclinical or early phases of clinical trials, is a particularly confounding complication of drug development. An understanding of the mechanisms that lead to idiosyncratic liver toxicity would be extremely beneficial for the development of new compounds. We used microarray analysis on isolated human hepatocytes to understand the mechanisms underlying the idiosyncratic toxicity induced by trovafloxacin. Our results clearly distinguish trovafloxacin from other marketed quinolone agents and identify unique gene changes induced by trovafloxacin that are involved in mitochondrial damage, RNA processing, transcription, and inflammation that may suggest a mechanism for the hepatotoxicity induced by this agent.”

Ultrastructural changes induced by the des-F(6)-quinolone garenoxacin (BMS-284756) and two fluoroquinolones in Achilles tendon from immature rats.   “Garenoxacin is a des-(6)-fluoroquinolone exhibiting a comparatively low chondrotoxic potential in juvenile animals. We studied the effects of the drug on Achilles tendons in immature Wistar rats treated by oral intubation once daily (1) for 5 consecutive days from postnatal week 4 onward at doses of 0 (vehicle), 200 and 600 mg/kg body weight (b wt), and (2) for 21 consecutive days from postnatal day 4 onward at doses of 0 (vehicle), 80, 240 or 300 mg/kg b wt; ofloxacin or ciprofloxacin were used as comparators. Achilles tendon specimens were studied by electron microscopy. In comparison with vehicle-treated controls, ultrastructural changes were detectable in all samples from the garenoxacin-, ofloxacin-, or ciprofloxacin-treated rats (one animal per group). We found degenerative changes such as multiple vacuoles and large vesicles in the cytoplasm of tenocytes that resulted from swelling and dilatation of cell organelles (mitochondria, endoplasmic reticulum), densified nuclei and clumped chromatin; furthermore, cells that detached from the extracellular matrix, a general decrease of the fibril diameter and an increase in the distance between the collagenous fibrils were recognizable. The degree of changes increased with increasing doses. It remains unclear what these findings mean with respect to a possible risk in juvenile patients treated with garenoxacin or the other quinolones, but our results underline the fact that, in principle, this des-(6)-fluoroquinolone also has the potential to cause changes in connective tissue structures.”

Lysosomal membrane permeabilization induces cell death in a mitochondrion-dependent fashion.   “A number of diseases are due to lysosomal destabilization, which results in damaging cell loss. To investigate the mechanisms of lysosomal cell death, we characterized the cytotoxic action of two widely used quinolone antibiotics: ciprofloxacin (CPX) or norfloxacin (NFX). CPX or NFX plus UV light (NFX*) induce lysosomal membrane permeabilization (LMP), as detected by the release of cathepsins from lysosomes. Inhibition of the lysosomal accumulation of CPX or NFX suppresses their capacity to induce LMP and to kill cells. CPX- or NFX-triggered LMP results in caspase-independent cell death, with hallmarks of apoptosis such as chromatin condensation and phosphatidylserine exposure on the plasma membrane. LMP triggers mitochondrial membrane permeabilization (MMP), as detected by the release of cytochrome c. Both CPX and NFX* cause Bax and Bak to adopt their apoptotic conformation and to insert into mitochondrial membranes. Bax-/- Bak-/- double knockout cells fail to undergo MMP and cell death in response to CPX- or NFX-induced LMP. The single knockout of Bax or Bak (but not Bid) or the transfection-enforced expression of mitochondrion-targeted (but not endoplasmic reticulum-targeted) Bcl-2 conferred protection against CPX (but not NFX*)-induced MMP and death. Altogether, our data indicate that mitochondria are indispensable for cell death initiated by lysosomal destabilization.. . . Lysosomotropic agents are lipophilic bases that accumulate in the lysosomal lumen and can exert detergent-like or local phototoxic effects on lysosomal membranes. Two quinolone antibiotics, norfloxacin (NFX) and ciprofloxacin (CFX), which are used on millions of patients each year, are lysosomotropic and can induce apoptosis either in the presence (NFX) or absence (CFX) of a low dose of UV light (1719). This property may explain the unwarranted cytotoxicity of such compounds (and, in particular, the deleterious effect of NFX medication plus sunlight exposure) and lead to the proposal that quinolone antibiotics could be used for cancer therapy.”

Suppression of human prostate cancer cell growth by ciprofloxacin is associated with cell cycle arrest and apoptosis.   “For hormone resistant prostate cancer (HRPC), chemotherapy is used but the mortality is 100% with a mean survival time of 7-8 months. Our previous studies have shown the chemotherapeutic effect of ciprofloxacin in bladder cancer. At doses 50-400 micro g/ml ciprofloxacin, the concentrations that are normally achieved at doses currently used for the treatment of anti-bacterial infections, inhibited bladder cancer cell growth and induced S/G2M arrest with modulation of key cell cycle regulatory genes and ultimately activated apoptotic processes . . . These results suggest the potential usefulness of the fluroquinolone, ciprofloxacin as a chemotherapeutic agent for advanced prostate cancer. The fluroquinolone ciprofloxacin showed anti-proliferative and apoptosis inducing activity on prostate cancer cells but not on non-tumorigenic prostate epithelial cells. These effects of ciprofloxacin were mediated by cell cycle arrest at S-G2/M phase of the cell cycle, Bax translocation to mitochondrial membrane and by increasing the Bax/Bcl-2 ratio in PC3 prostate cancer cells. Based on our in vitro results, further in-depth in vivo animal or human investigations are warranted.”

Ultrastructure of Achilles tendon from rats after treatment with fleroxacin.   “Quinolone therapy can be associated with tendon disorders (tendinitis, ruptures), but little is known about possible ultrastructural changes in tendons after exposure to these antimicrobials. We studied the Achilles tendons from fleroxacin-treated adult rats by electron microscopy . . . we were able to detect pathological changes even at the lowest dose level (30 mg/kg), which increased in incidence and severity with increasing doses. Tenocytes exhibited degenerative changes such as multiple vacuoles and large vesicles in the cytoplasm that resulted from swelling and dilatation of cell organelles (mitochondria, endoplasmic reticulum). The nucleus became dense and the chromatin had clumped to form rough plaques. The cells detached from the extracellular matrix. Other important findings were a general decrease of the fibril diameter and an increase in the distance between the collagenous fibrils. The finding that these rather low single dose of a fluoroquinolone induce ultrastructural changes in Achilles tendons from rats, which were not associated with clinical symptoms and which were still present 4 weeks after treatment, is of concern. Further toxicological as well as clinical studies are needed to characterize the conditions under which quinolone-induced tendon lesions develop.”

Damage to mitochondria of cultured human skin fibroblasts photosensitized by fluoroquinolones.    “The phototoxic fluoroquinolones ofloxacin, lomefloxacin, norfloxacin, ciprofloxacin and BAYy 3118 have ionizable groups with pKa values close to neutrality. Different ionic species of these fluoroquinolones, therefore, partition in various compartments and organelles of living cells according to their ionic equilibria. While all these fluoroquinolones accumulate in lysosomes, they more or less stain the rest of the cytoplasm of living HS 68 fibroblasts. As a result, photosensitized damage to other cytoplasmic sites than lysosomes can also be expected. Using microfluorometry and rhodamine 123 (Rh 123) as a specific fluorescent probe which is released from mitochondria by light absorption, we show that under ultraviolet A (UVA) irradiation norfloxacin and ciprofloxacin readily damage mitochondrial membranes. as evidenced by the UVA dose-dependent strongly accelerated release of Rh 123 from mitochondria in cells treated with norfloxacin and ciprofloxacin. Damages are already noticeable at UVA doses as low as 2 J/cm2 . . . The initial photodamage induced by norfloxacin and ciprofloxacin can then propagate after the irradiation as shown by the strongly increased rate of release of Rh 123 from mitochondria of cells that have been incubated with these two fluoroquinolones and left in the dark after a pre-irradiation with 18 J/cm2 of UVA.”

Influence of ofloxacin on chloroplasts and mitochondria in Euglena gracilis.   “Ofloxacin (CAS 83380-47-6), a representative of new quinolones, which exerts inhibitory activity against DNA gyrase in bacteria, damages both semiautonomous organelles in Euglena gracilis: chloroplasts and partly mitochondria. The action of ofloxacin on these organelles was analysed by transmission electron microscopy. The first symptoms of ofloxacin treatment were mass aberrations of chloroplasts with subsequent diluting out of these pathological organelles from the cells, so giving rise to the heterotrophic mutants. The loss of chloroplasts is hereditary. Changes in ultrastructure of mitochondria were observed too. Cup-like (in sections ring-like) mitochondria represented the most frequent abnormalities of these organelles induced by the drug. After repeated subcultivations on ofloxacin-free media the number of damaged mitochondria gradually decreased to the normal.”

4-Quinolones cause a selective loss of mitochondrial DNA from mouse L1210 leukemia cells.   “The 4-quinolone antibiotics nalidixic acid and ciprofloxacin are potent inhibitors of the bacterial type II topoisomerase DNA gyrase. Treatment of mouse L1210 leukemia cells with these drugs resulted in a delayed inhibition of cell proliferation. Prior to inhibition of cell proliferation, there was a time-dependent decrease in the cellular content of mitochondrial DNA (mtDNA). The decrease in mtDNA was associated with a decrease in the rate of mitochondrial respiration and an increase in the concentration of lactate in the growth medium. Inhibition of cell proliferation by 4-quinolones was reversible upon drug washout. However, there was a 2- to 4-day lag before the growth rate returned to normal levels. This was preceded by an increase in mtDNA content and mitochondrial respiration. These studies suggest that inhibition of mammalian cell proliferation by 4-quinolone drugs is related to the selective depletion of mtDNA.”

Chondrotoxicity of quinolones in vivo and in vitro.   “Chondrotoxicity is a rare toxicological finding which is observed in dogs after administration of quinolone antibacterials. To study this effect chondrocytes from articular cartilage of dogs were isolated, and incubated with quinolone derivatives. The effects on cell viability, mitochondrial dehydrogenase, and proteoglycan synthesis were determined. These results were compared with in vivo findings in dogs treated with these quinolones. It was concluded that inhibition of mitochondrial dehydrogenase activity and of proteoglycan synthesis are major reasons for cartilage damage.”


NMDA (N-methyl-D-aspartate), GABA (Gamma-aminobutyric acid) receptors, ACh (Acetylcholine)-related)       

FQs have long been implicated in potentially affecting the NMDA and/or GABA receptors as a cause for the extreme CNS symptoms they can cause.   The CNS symptoms are no joke.   In my opinion, there are no words in the English language to describe what flox victims go through when they are hit hard by the “CNS symptoms”.    Unfortunately, the word “anxiety” is the word most often used, which tends to give the impression that we’re “just a little anxious” and if we just meditate enough, or “calm down enough”, we can control these symptoms.    Nothing can be further from the truth.     You wouldn’t inject a strong dose of heroin into a person and expect them to not feel the effects, or to just “perk up and the drug won’t affect your receptors if you just think they won’t”.    You wouldn’t give a whopping dose of LSD to someone and expect them to go about their day normally, without any hallucinations, because they can “will them away”.    Such is the power of receptors, and the drugs that activate or block them.    And for those of us susceptible to FQT/FQAD, it is no different.

You also wouldn’t expect an addict to quit cold turkey from a severe, long term, drug or alcohol dependence to not feel any withdrawal symptoms, and tell them to “just get over it”.    Yet, this is exactly how most flox victims are treated when they end up in the ER with symptoms of “anxiety” after taking an FQ.    For example, in the case of FQT/FQAD, we appear to be suffering from severe withdrawal of the normal and necessary amount of physiological GABA, a “calming” neurotransmitter, leaving an excess of glutamate, an “excitatory” neurotransmitter”.   This same lack of GABA is thought to be an underlying mechanism in alcohol withdrawal syndrome and benzodiazepine withdrawal syndrome, responsible for some of the symptoms.   Entire detox programs exist to help alcoholics and addicts deal  with the delirium tremens, sleep disturbances, irritability, increased tension and anxiety, panic attacks, hand tremors, sweating, difficulty with concentration, confusion and cognitive difficulty, memory problems, dry retching and nausea, weight loss, palpitations, headache, muscular pain and stiffness, a host of perceptual changes, hallucinations, seizures, psychosis, suicidal thoughts, and more .    Yet, for those of us susceptible to FQT/FQAD, this is exactly what we go through as the FQs damage the receptors to lifesaving and sanity saving hormones and neurotransmitters, for days, weeks, months at a time, sometimes with no end in sight.   If we make it through the acute state, we’re often left with insomnia, anxiety, depression, panic attacks, brain fog and/or cognitive impairment, depersonalization and/or derealization, psychoses, and suicidal ideation.   And there is no treatment center, no drugs to help us, certainly no empathy or understanding, and not even any acknowledgement by the medical or psychiatric establishment that this is, in fact, what we are going through.

As if this weren’t enough, I think that the CNS symptoms are multifactorial for many of us, which is what makes them even more horrific.   In “Intra-cranial Pressure and Headaches” I provide case reports of infants being given nalidixic acid, the precursor to the FQs, and exhibiting brain swelling clearly evidenced by bulging fontanelles, papilloedema, and widening skull sutures.    Although this alleviates the CNS pressure for infants, it’s not an option for the rest of us with closed fontanelles and sutures, who scream in agony to a disbelieving medical profession.   In “Acetylcholine (ACh) – Related Damage“, I discuss the severe CNS and “psychiatric events” which can occur with the cholinergic and anticholinergic delirium syndromes, which are potential mechanisms to consider in FQT/FQAD but also remain unrecognized and unacknowledged by the medical profession.   In “TSH and T4: Useful or Useless?” I discuss how fluctuating hormones and anti-thyroid antibodies can also cause severe CNS symptoms and “psychiatric events”, including psychoses, also often unrecognized by physicians.   In my case, I discovered/developed Hashi’s post FQ, and have high enough antibody titers that Hashi’s Encephalopathy is a real consideration.   Here, on top of all those other effects and probably more, the FQs have been shown to interact directly with and potentially damage the NMDA and GABA receptors as well, accounting for the long term or permanence of some of these reactions.   These various factors probably contribute to the range of severity and duration of CNS symptoms that victims of FQT/FQAD experience.

Glutamate, GABA, and all the other neurotransmitters are incredibly important, not only for our brains, but for all our nervous tissue and numerous non-neuronal cells too.   Antibiotics which are supposed to be targeting “only bacteria” should under no circumstances be targeting these human neurotransmitter receptors so necessary for our well being and lives.   With an estimated 27 million prescriptions for these antibiotics being written each year, and an estimated 10% of patients taking them experiencing CNS side effects, that’s a lot of CNS symptoms (2,600,000 CNS adverse events per year due to FQs alone) out there.    And those are only the recognized and reported ones; that number could be much higher.   Given the FQs propensity for further delayed effects and ongoing damage and deterioration, we really have no idea how much FQs are contributing to the huge burden of psychiatric illness, such as depression and mental illness, overall.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.    But for anything and everyone else — why take the risk?

References 11:   References for FQ-Induced Neurological Symptoms, implicating NMDA/GABA receptors and MG/ACh mechanisms;  Glutamate/NMDA and ACh implicated in Tendinopathies.  These are the same references mentioned in “Glutamate/GABA – Related Damage” and in the Dear Dr Neurologist letter.


Dysglycemia related targets (HERG K channels, K-ATP channels, histamine release from mast cells, glucagon-like peptide 1 (GLP-1), glucose transporter type 1 (GLUT1), and more):    Unintentional Targets / Adverse Effect  

Dysglycemias are abnormal blood glucose levels from any cause that contribute to disease.   This is most often seen in the form of Diabetes Mellitus, in particular, Type 2 Diabetes.   Diabetes of any type is a huge, global worldwide epidemic.   Although there appears to be a genetic component, environmental or lifestyle factors appear to play a large role.    More importantly, the “genetic” aspect of diabetes is now thought to include an “epigenetic” factor  in nature, meaning your parents and grandparents diet and eating habits (and their parents and grandparents diet and eating habits) will affect you and your children.   With the explosion of access to all kinds of processed, insecticide-laden, genetically modified food in the past fifty years that the human body hasn’t seen in the millions of years we’ve been evolving, this may be bad news for future generations.   Nature usually takes millions of years to evolve to new insults.  The epigenetic modifications allow faster adaptations to occur, within a few generations.   But I don’t think even that will be fast enough for the human race to adapt to the onslaught of all the pollutants and toxins we’ve been exposing ourselves to, and continue to expose ourselves to, on a daily basis.   There is increased awareness and concern about “External Climate Change” now.   But I don’t think enough of that same concern and awareness has developed when it comes to our “Internal Climate Change”.   And the “diabetes epidemic” is just one excellent example of that.  Young adults and children are being diagnosed at younger and younger ages in epidemic proportions.   I sometimes wonder if people 100 years from now will ever remember a time when people were not born diabetic.

When it comes to diabetes, the “sugar industry” will blame it on fats, the “fat industry” will blame it on sugar and carbs, the organic food industry will blame it on processed foods, the fitness industry will blame it on lazy-ass couch potatoes, and thin people may blame it on fat people.    But almost no one seems to consider the astounding number of pharmaceutical drugs we put in our bodies throughout our lives with proven dysglycemias as a “side effect”, see:    “Drug Induced Diabetes”,   “Drugs that Affect Blood Glucose”, and  “Drug-Induced Hyperglycaemia and Diabetes“.    And never one to be left out of a serious side effect, that includes the FQ antibiotics.

Fluoroquinolones have been associated with severe, even life threatening dysglycemias.  This includes both hypo and hyper glycemia.   Although all FQ’s have this potential, the poster child for this is the FQ Gatifloxacin, which  was withdrawn from the market in 2008 due to life threatening dysglycemias, including “fatal events”.   I also developed marked dysglycemia from the Cipro I took, with blood glucose values swinging from 50 – 250 mg/dL during the acute phase, and eventually “settling in” at Type 2 Diabetes.   I think the scarier thing was the severe “cerebral hypoglycemia” I appeared to experience, despite normal serum glucose levels as tested with a glucometer.   I had numerous episodes of fairly rapid onset  of practically feeling comatose, stumbling around, disoriented, shaky, weak, feeling like I was going to pass out and die – and then eating a cookie, or simply taking a teaspoon of sugar – and within 10-20 minutes feeling remarkably better.   I managed to test my glucose levels despite feeling half dead before eating the cookie or glucose, and values were always within normal ranges.   Given that glucose alone seemed to really help, and with the type of symptoms I was experiencing, I can only hypothesize that for some reason (most likely a receptor/transporter dysfunction?), I simply wasn’t getting enough glucose into my brain cells.  These were scary episodes, and stopped once I made sure I was eating carbs every several hours every day.   This is also one reason the “Paleo Diet” was so devastating for me.    As with everything else going on with me since being floxed, “It Feels Like a Homeostasis Issue”.   I have to eat the right amount of carbs, in the right amounts, at the same times each day, in order to maintain “glucose homeostasis” levels symptomatically for my brain, while not testing too high in serum levels with my meter as well.

Glucose metabolism is intimately and intricately intertwined with every other hormonal and neuroendocrine system.  This is why diabetes is not “simply a blood glucose level” problem, but the gateway to all kinds of additional problems involving high blood pressure, high cholesterol, heart disease, vascular disease, stroke, kidney disease, neurological disease, sexual dysfunction, blindness and eye disease, foot complications and amputation, tendon disorders, skin infections and disorders, hearing loss, periodontal disease, GI disease, increased probability of death, and more.

Diabetic neuropathy is one of the more well known complications of diabetes as well. From Wiki Diabetic Neuropathy:    Globally diabetic neuropathy affects approximately 132 million people as of 2010 (1.9% of the population).   Diabetes is the leading known cause of neuropathy in developed countries, and neuropathy is the most common complication and greatest source of morbidity and mortality in diabetes patients.   It is estimated that the prevalence of neuropathy in diabetes patients is approximately 20%.   Diabetic neuropathy is implicated in 50–75% of nontraumatic amputations.

FQs are well known to cause long term and permanent neuropathy, and in fact, the FDA required label changes in 2013 to reflect this:

FDA Drug Safety Communication:    FDA requires label changes to warn of risk for possibly permanent nerve damage from antibacterial fluoroquinolone drugs taken by mouth or by injection (8/15/13 update).    “The U.S. Food and Drug Administration (FDA) has required the drug labels and Medication Guides for all fluoroquinolone antibacterial drugs be updated to better describe the serious side effect of peripheral neuropathy.   This serious nerve damage potentially caused by fluoroquinolones may occur soon after these drugs are taken and may be permanent.”

Given that FQs can cause both severe dysglycemias as well as severe peripheral neuropathy, it doesn’t seem like a very good idea at all to pass these drugs out nonchalantly as a “first choice drug” for anything.   Tendon issues can also be a complication of diabetes, and I include a few studies for that as well in the references below.

In “Glucose and Insulin Related Testing”, I said the following:

As with most everything else, diabetes appears to be caused by a combination of genetic and environmental or lifestyle factors.   For the lifestyle factors, exercise and food choices are the two biggies.   In addition, if you want to greatly decrease your chances of getting diabetes, do three things:

1) Don’t take an FQ antibiotic

2) Don’t take any other prescription drugs with diabetes as a “side effect” (see here, here, here, and look up any drug you are about to take).

3) Buy a glucose meter and strips, test regularly to see where you are on the “glucose continuum”, and avoid the foods that spike you or keep you high.

Diabetes is a growing epidemic with a devastating physical, emotional and financial toll in this country and globally.   It kills more Americans each year than AIDS and breast cancer combined.

If you have cancer, or are on your death bed due to sepsis nothing else will get, you might want to consider an FQ.   But for anything and everyone else — why take the risk?

References 15 :    FQ-Induced Dysglycemias and Diabetes; Diabetes and Tendon Disorders


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