Why I Caution the Use of the Antibiotic Flagyl (Metronidazole)

Why I Caution the Use of the Antibiotic Flagyl (Metronidazole)

There are many different medications that are being frequently used where doctors are unaware of the potential severe side effects that are associated with their use. The antibiotic Flagyl (metronidazole) is no exception. The antibiotic is very cheap and it is on the World Health Organization’s List of Essential Medicines (meaning it is believed to be effective and safe). Doctor’s prescribe it daily around the world without alerting their patients to the complications that are caused by the antibiotic and how to potentially protect them from unwanted side effects if its use is needed. I recommend that before you ever take a medication prescribed to you (unless it is an emergency situation) ask your doctor if they have ever read the medication insert for your prescribed medication. If they say no, then you should probably read it yourself so you know more about the efficacy and risks of the prescribed medication and maybe find yourself another healthcare professional that takes the time to research what they prescribe. So what are the known serious side effects with Flagyl and what can be done to attempt to protect yourself from them if you have to take the antibiotic?

All About Flagyl

Flagyl is a frequently prescribed antibiotic of the nitroimidazole class and it inhibits nucleic acid synthesis by disrupting the DNA of microbial cells. Flagyl has antimicrobial activity against Gram positive and negative anaerobic bacteria (Bacteroides, Fusobacterium, Clostridium, some susceptible strains of Eubacterium, Peptostreptococcus, and Prevotella for example) and some parasites. Flagyl has little to no antimicrobial activity against aerobic bacteria. Flagyl is used for mild to moderate C. difficle and parasitical infections. It is useful against the parasites Dracunculus medinensis, Giardia lamblia, Trichomonas vaginalis, and the Entamoeba genus.

There are many different known side effects associated with the medication. These side effects range from the common gastrointestinal upset associated with antibiotics to neuropathy, cause or worsen seizures, increased risk of Stevens-Johnson Syndrome when combined with mebendazole, brain lesions, aldehyde enzyme down-regulation, and immune system suppression. Flagyl should not be used in people who suffer from Crohn’s disease because of the potential chromosomal abnormalities in circulating lymphocytes in people treated with metronidazole potentially leading to cancer. If you are suffering from liver disease then you want to make sure that your doctor monitors you for increased Flagyl associated side effects because of hindered metabolism. The following images are Flagyl drug insert warnings associated with the antibiotic that I believe are important for your decision whether or not to take the medication.

Flagyl is also reasonably anticipated to be a human carcinogen per the National Toxicology Program but forth by the Department of Health and Human Services, though studies of its carcinogen potential are mixed.

Flagyl use is not studied extensively for pregnant women and is known to cross the placental barrier and is secreted into human breast milk as well. The Flagyl drug insert states that it should be cautiously used in pregnant women because when given intraperitoneally it has caused intrauterine infant deaths and since it is an unknown carcinogen that it might trigger mother and fetal cancer development. Its potential carcinogenicity is also why it is not recommended in use for breast feeding mothers because it is secreted into human breast milk. Finally, the antimicrobial is not recommend for pediatric use because its safety and effectiveness has not been established, except when used for the treatment of amebiasis.

What Are Aldehyde Breakdown Enzymes and Why Do They Matter?

Aldehyde oxidase and aldehyde dehydrogenase are enzymes are produced by the body to metabolize aldehydes. These enzymes are encoded by nineteen ALDH genes. Aldehydes are many different compounds, including formaldehyde and acetaldehyde. We encounter many different aldehydes throughout our daily life, and they differ in their toxicity.1

Alcohol metabolism produces acetaldehydes which further have to be metabolized to prevent oxidative stress and alcohol poisoning. If we are not able to detoxify alcohol correctly its consumption easily becomes deadly.2

Consumption of alcohol requires ample amounts of aldehyde oxidase and aldehyde dehydrogenase to convert acetaldehydes produced from ethanol detoxification by the liver into carboxylic acids including acetic acid that can be utilized or eliminated from the body. Though our body produces aldehydes through normal metabolism processes if our body is not able to detoxify them properly health issues occur. We also ingest acetaldehydes from other food sources including coffee, bread, and ripened fruit it differing amounts, however, it is less than ingestion of alcohol. Without these enzymes, alcohol consumption becomes quite toxic. For example, the medication disulfiram was developed to help treat alcoholism by interfering with the functionality of aldehyde detoxification enzymes, mainly acetaldehyde dehydrogenase. After alcohol intake under the influence of disulfiram, the concentration of acetaldehyde in the blood may be five to ten times higher than that found during metabolism of the same amount of alcohol alone. When a person consumes alcohol while using disulfiram they develop symptoms similar to mold sensitivity including headaches, brain fog, visual disturbances, elevated heart rate, face flushing, allergic reactions, nausea, vomiting, and shortness of breath. Many of the symptoms are similar to a bad hangover. If enough alcohol is consumed the symptoms can intensify from a severe hangover to coma and eventually death from aldehyde poisoning. Finally, disulfiram is slowly metabolized by the body and can take up to two weeks before its effects on blocking acetaldehyde dehydrogenase stop.3 4

Some people have gene polymorphisms that cause the body to encode less of these enzymes and are even more prone to the effects of acetaldehyde. ALDH2 is one of these genes that helps encode acetaldehyde dehydrogenase and is tested if you get a 23 and Me genetic test and it is a gene that helps encodce . Fungi and yeast produce aldehydes that require these enzymes to help us detoxify them. People using these medications or have an ALDH2 polymorphism might be more sensitive to mold toxicity.5

Does Flagyl Increase Mold Sensitivity?

Flagyl like the medication disulfiram may reduce the body’s ability to produce aldehyde detoxification enzymes. The inhibition of these enzymes is the reason why alcohol is strongly discouraged in people who are taking Flagyl for infections. The same can be said for individuals who have mold sensitivity issues, yeast overgrowth, or live in moldy environments.6 7 8

Flagyl supposedly inhibits the production of aldehyde detoxification enzymes within our cells and affects our mitochondria and liver function. It is possible that if you needed to take Flagyl and suffer from fungi issues, molybdenum may help increase enzyme production or at the bare minimum help you maintain proper levels of the mineral when you stop the medication so that proper enzyme levels can be up-regulated by the body. The body uses molybdenum to produce aldehyde detoxification enzymes. 9 10 11

There are however a few studies that do cast doubt in Flagyl causing a reduction of aldehyde detoxification enzymes in people who have proper enzyme levels or people that do not have genetic predispositions to lower enzyme potential. One study indicates that the side effects from Flagyl are not from inhibiting aldehyde detoxification enzymes but instead are from the medication producing serotonin syndrome in some people. Another study indicates that the side effects of Flagyl that mimic aldehyde detoxification issues maybe from the microbiome shift caused by the antibiotic. 12 13 14

So it would be my recommendation as well that if the serotonin increasing mechanisms of Flagyl are correct that people taking SSRI’s, 5-HTP, or anything that increases serotonin to talk with their doctor and use caution when using Flagyl.

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