From a Patient’s Perspective…

Woman_Falling_ApartI created this blog for one simple purpose—to help people who have had a serious, adverse reaction to Flagyl (aka, metronidazole), so they have a place to read about the condition and to answer questions that no medical professional was willing to help me find.  What you have has a name: Metronidazole-induced Central Nervous Toxicity (or metronidazole toxicity for short).

I am not a doctor; I was a patient.  All of my posts are based on my personal experience and information I found across the internet.  You will have to decide what to take from this site, but I hope it helps you through your recovery.

I haven’t had time to update this page.  Make sure to check out “Treatment” that will go into more detail about the mechanism behind metronidazole toxicity and ways to possibly improve symptoms!

Here is the quick sum-up of my experience with metronidazole:

In June of 2015, I was diagnosed with c diff (a gut bacteria), and prescribed metronidazole, 500mg.  Six days into taking it, I had a serious, adverse reaction, including difficulty walking, slurred speech, dizziness, extreme fatigue and feeling faint.  What followed was six weeks of debilitating fatigue, brain fog, depression, severe insomnia, muscle twitches, nausea, zero appetite, coughing, difficulty swallowing, shortness of breath, brain zaps (feels like lightning bolts surging through my skull), flushing face, chills, hand tremors, neck pain, and the absolute worst anxiety I’ve ever experienced (sound familiar?).

But what was worse was that the doctors flat-out did not believe me.  They insisted that the antibiotic was “out of my system” less than a week after my last dose; therefore, it couldn’t be the drug.  Of all the things that happened to me, this was the most disheartening, and if you are suffering from the same situation with your doctors, I am so sorry.  I hope that this website helps you better understand what you have and what to expect.

Now, over four years later, most of my symptoms have resolved and the ones that are minor and infrequent.  I’m enjoying life again.  The first two months were the hardest, and it slowly improved over about nine months, and then, when introducing the treatment plan listed on the Treatment page, things really turned around.

Most of all, this experience has left me disillusioned by the health care system.  If you are experiencing even some of the symptoms I’ve addressed, you are probably experiencing some form of metronidazole toxicity.  Your doctors don’t believe you—I do.  I believe you because I went through it, researched it, and now, I want you to have an easier time than I did in knowing what this condition is about.

If you wish to learn more about my experience with metronidazole toxicity and how the medical community responded, I have an article published in the online magazine Hormones Matter:

Metronidazole Toxicity and Doctor Denial


The Most Common Questions I had while Dealing with Metronidazole Toxicity

  1.  Will I recover from metronidazole toxicity?

Most likely, yes.  While you certainly feel awful right now, the prospects for recovery are good and (for most people) seem to come soon after discontinuation of the drug.  People who are suffering from mood changes only are especially more likely to recover completely.  People who suffer from motor control problems (difficulty walking, slurred speech, etc) or autonomic dysfunction (aka, issues with the “automatic” operations in the body like breathing, heart rate, digestion), have a slightly less chance of complete recovery but it’s still the outcome for the majority of patients.  If nothing more, you should greatly improve over time.

  1. What is happening that’s causing this adverse reaction?

Essentially, metronidazole has no problem getting past the “blood-brain barrier.”  This is a dense set of cells that doesn’t let some substances cross from the body to the brain; as an example, the drug imodium cannot pass this barrier, which is why you will rarely see a review about it causing mental issues.

Metronidazole easily goes to your barrier, and an adverse reaction means that it is causing dysfunction (and sometimes lesions) on your brain.  The lesions are only detectable through an MRI and documented cases show they are visible in 93% of patients who were suspected to have metronidzaole toxicity (see source here or download the entire article, click metronidazole-neuropharmacol-2011-article).  

However, this information needs to be taken lightly, as lesions have been found to be less common with metornidazole toxicity sufferers, as patients who have metronidazole toxicity but don’t present with lesions rarely have their case reports published or documented.  This leaves a skewed view that the lesions are more common and a misguided test for doctors to depend on when diagnosing the toxicity.  In other words, you don’t have to have lesions to be suffering from metronidazole toxicity; symptoms are be used to diagnose instead.

If you have the lesions, they typically quickly after discontinuation of the drug in 83% of patients, so they are usually reversible.  They are found mainly on the cerebellum, followed closely by the brain stem (and sometimes the basal ganglia).

There are five tell-tale signs of metronidazole CNS toxicity in medical literature:

  • Dysarthria (slurred speech and/or dysfunction of speech patterns)
  • Ataxia (motor control problems, usually presented as difficulty walking–not numbness, tingling or burning, but the actual inability to coordinate your legs).  Arms and also eye movement can be affected as well.
  • Dizziness
  • Seizures–more prominent in older patients.
  • Altered Mental State–more prominent in younger patients.

While the “altered mental state” is subjective, from everything I’ve read, it’s usually described as mental confusion, severe anxiety, and/or depression.  Personally, I could not calm my body down (see my page on Anxiety here), but was always cognitively aware of time and place.

In addition to these documented issues, metronidazole toxicity can also cause autonomic dysfunction.  This is due to issues of the brain stem, which controls all the “involuntary” operations of the body.  These include issues with:

  • Digestion (usually constipation, but it can be diarrhea)
  • Anorexia (complete loss of appetite / will to eat)
  • Heart Palpitations
  • Irregular Blood Pressure
  • Difficulty Swallowing
  • Dysfunction of Salivary Glands (can cause white tongue / white patches)
  • Temperature Deregulation 
  • Respiratory Issues (asthma-like breathing problems)
  • Frequent Urination
  • Emotional Lability (dysfunction of fight-or-flight response)

There is little medical literature on autonomic dysfunction (aka, dysautonomia) due to metronidazole toxicity; however, the drug can cause damage to all regions of the brain stem: the pons, medulla and midbrain.  In addition, we have a support group on Facebook, and more patients complain about dysautonomia due to metronidazole than cerebellar dysfunction.  And I have dealt with most of these autonomic-issues myself.

Metronidazole can also cause polyneuropathy, which is burning, tingling and/or numbness in your body, especially hands, feet and/or face.  It can also cause optic neuropathy, which can impair vision.

  1. How long will it take me to recover?

This is a really tricky question.  I’ve looked at many patient reviews and most people share their initial experience, but never follow-up after.  Even in case studies, the time frame is difficult to measure because most doctors don’t follow patients more than 3 months after discontinuing the drug.

That being said, from best I can gather from reviews and case studies, people either have a resolution of all symptoms (65%) or show improvement 3 months after their initial reaction (29%).  That’s medical literature, but after over 2 years of doing research myself and listening to metronidazole sufferers, here’s what I’ve learned:

Flare up’s are unfortunately common.  Since June 2015, I’ve had several mild flare up’s and 2 major ones, including one in November of 2017.  It was at this time that I happened upon a new medical textbook called “Thiamine Deficiency Disease, Dysautonomia, and High-Calorie Malnutrition.”  Looking back at my own research, it became clear that metronidazole destroys the thiamine (aka vitamin B1) in your body; when you are deficient in thiamine, you have:

  • Cerebellar Dysfunction (cerebellar dysfunction)
  • Autonomic Dysfunction (brain stem dysfunction)
  • Altered Mental State
  • Polyneuropathy

Thiamine deficiency can even cause lesions on the back of the brain, and medical literature is continuously compared metronidazole toxicity and another type of neurological disorder, Wernicke’s Encephalopathy, due to their striking similarities in symptoms and the appearance of brain lesions.  Wernicke’s is directly caused by thiamine deficiency.

You cannot correct a deficiency this great by just eating thiamine-rich foods; it requires months of high-thiamine supplementation and magnesium supplementation.  But this is actually good news, because this means that if you are having metronidazole toxicity issues like flare up’s, there’s something you can do about it!  

Please visit my “Treatment” page to learn more and get your quality of life back!

  1. Will I have a relapse?

Most people will not have a full relapse, but flare up’s are common.  I‘ve looked into this phenomenon quite a bit (reading case studies and page after page of patient reviews) and most people don’t complain about a delayed reaction or relapsing after the first reaction and discontinuation of metronidazole.  For most patients, the reaction seems to come on during administration of metronidazole and lessens after discontinuation until it either improves or disappears altogether.

This is not the case with everyone.  There is a possibility of a relapse in a small number of patients I’ve talked to directly; it usually happens within the first year.  It is rare but it can occur.

My theory is that this is due to issues with thiamine (and magnesium), and again, you can learn about this condition on my Treatment Page.  A relapse is possible if the thiamine deficiency is not properly addressed and corrected.  The treatment is cheap and you can start TODAY (I’m not getting paid a cent, by the way–I just want you to get better as I have).

And the most mind-numbing question of all…

  1. Why won’t my doctors believe me???

This is probably the most frustrating thing of this whole situation; you know you’re not well.  You know you’re not yourself—the anxiety, the fatigue…you feel like you’re dying sometimes, and your doctor refuses to accept that this could be due to the drug.  They might even refuse tests or insist you’re mentally ill, with or without a previous medical history of mental illness.  I went through this myself and it is terrifying.

Here is the bottom line—doctors are not trained to recognize, diagnose and treat adverse drug reactions.  Again, doctors are not trained to diagnose and treat your condition.

Adverse drug reactions are responsible for 100,000 deaths in the US every year.  This does not include the 20,000 people who die from illegal drug use; this does not include those who abused or used their prescription drugs incorrectly (a death rate that has drastically increased recently due to the opiate crisis–this number does not represent those patients).

—I want to emphasize here that, with all the research I’ve done on metronidazole toxicity, I’ve only found two people who died due to its effects.  One was a rare case of liver function issues, nothing to do with the brain, and while the other was due to metronidazole toxicity, but at very high doses through an IV.  The patient continued treatment for over two weeks after toxicity symptoms began.  So can it happen?  Yes, but it seems to be rare and if you stopped taking the drug, is highly unlikely.

The harm caused by drug reactions has been called the “silent epidemic” due to the mortality numbers (and those left permanently disabled) challenging that of Alzheimer’s patients and many other common, life-threatening conditions.  Twice as many people die from adverse drug reactions each year than those who die in car accidents.

And yet, there is no mandate for doctors to report an adverse drug reaction to the FDA.  Even if they suspect or have even confirmed a diagnosis, reporting those effects is 100% voluntary.  Due to this lack of regulation, only 1% to 10% of adverse drug reactions are reported (10% being a really optimistic number).

This is why doctors do not believe a drug can cause such harm to their patients.  Not only are drugs their top weapon to combat disease, but doctors also lack the education to understand just how dangerous prescription (and even non-prescription) drug can be.  Because there is no regulation, they are misinformed about the dangers, and we, the patients, suffer the consequences of their ignorance and denial.

This isn’t entirely their fault, however.  It’s part of a larger problem.  Let’s break it down.

The FDA:  The FDA is directly funded by the pharmaceutical companies, not taxpayer money.  A quarter of all FDA employees will end up working for a pharmaceutical company.  There are thousands of employees at the FDA who are there to approve new drugs; there are–literally–about 50 employees there who monitor the over 3,000 drugs currently on the market.  They are underfunded, understaffed and their money comes from the companies they are supposed to regulate.

The Pharmaceutical Companies:  As for the pharmaceutical industry, they give a lot of money to medical universities.  At Hazard, there is a lecture hall named after Pfizer, Inc. (one of many medical buildings named after pharmaceuticals).  Many medical journals, including the Journal of the American Medical Association, advertise and take money from pharmaceuticals.  And when these companies conduct their clinical trials on new drugs, they do not have to disclose any trial to the FDA where the drug failed to work better than placebo (aka, a sugar pill).  They have the right to conduct 30 trials on a drug, and only disclose the 3 trials to the FDA where the drug happened to work better.

For every nine doctors, there is one pharmaceutical sales rep, and when doctors take gifts from sales reps, those doctors are six times more likely to prescribe new, more expensive drugs to the patients.  This problem is so widespread that even our current Congress (yes, 2017), put restrictions on it due to the corruption.

Of course, there is the strange mentality that doctors are just too plain smart to be influenced by “Big Pharma” and that advertisements and gifts only work on us stupid people.  In the US every year, the pharmaceutical companies spend 4 billion dollars marketing directly to patients (and if it didn’t work, they wouldn’t do it, right?).  They spend 23 billion dollars marketing directly to doctors.

To learn more about this phenomenon, watch the video below–it sums it up quite nicely.

Even if a doctor doesn’t give in to marketing ploys, they are still dealing within a group of peers who regularly do.  They are taught the benefits of drugs, and the adverse effects of them are either glossed over or omitted completely.  The only doctors who seem to understand this issue are ones who have experienced a drug reaction themselves.

The Human Factor.  In addition to the issue above, there is a basic, human element at work here.  Everyone, including doctors and patients, believe that drugs are supposed to heal.  That is their only purpose.  So when a drug not only doesn’t work, but actually harms…this causes a phenomenon called cognitive dissonance.  It creates a contradiction in a person’s thought process “The drug is meant to help, so how can it have caused harm?”  This contradiction causes psychological stress–it threatens the person’s belief and can lead to another issue, “Identity Protective Cognition.”

Here is a lighthearted video about this affect:

Telling a doctor (or anyone) a trivial correction to their thought process is one thing–most people can handle being slightly wrong.  But doctors exist to help their patients recover from disease or injury, so when you tell a doctor their treatment harmed you instead of healed you, you are threatening their identity.

Doctors really do want to help their patients, but just like all humans (including you), they are more interested in protecting themselves.

Therefore, it’s easier to deny the problem or even gaslight the patient (“You’re not sick from this drug I gave you!  You’re just an anxious and depressed person.”).  This is a recipe of a toxic situation, especially when you, the patient, are dealing with a serious medical condition that needs treatment and have no real power in the medical hierarchy to change minds that don’t want to listen.

This is especially difficult if you are dealing with an adverse drug reaction that causes psychiatric symptoms such as depression and anxiety.  It is difficult to test and diagnose, and if physicians cannot find anything physically wrong with you, they can easily assume it’s “all in your head.”

I wish I had a good solution here for this problem.  The only thing I can say is this—it is NOT you.  It is the drug.  And it will get better.  You will have to be patient with yourself and know that you’re not the problem.  You are right—they are wrong.  It’s as simple as that.

I hope this helps you as you continue to recover from this horrible reaction.  I want to say again that I’m so sorry you’re going through this, and I wish you the best in your recovery.

Sources for this blog post:

  • To learn more about metronidazole toxicity, click here for the link to a accumulative case study (it’s where a lot of my information came from).
  • Here is another link to another study–click here.
  • Here’s another one: click here.
  • Another:  click here.
  • Another case (this one talks about longer resolution of all symptoms, so it’s beyond 3 months out for you, there’s still hope of recovering completely).  Click here.
  • To see that you are NOT alone, visit to see other people’s experience going through this horrible reaction.  There are two main listings there, one for Flagyl (the brand name) and one for metronidazole (the generic name).
  • For information about adverse drug reactions in general, click here.
  • “When Medicine Hurts: The Silent Epidemic” – click here.
  • “The Epidemic of Silence with Adverse Drug Reactions” – click here.

I plan to post more on here as time goes on.  I hope at least this first post gives you a better understanding of what metronidazole toxicity is, and maybe helps to relieve some of your anxiety in at least knowing you are not alone in your struggle.

Feel better!  My heart goes out to you!