This is the need-to-know information for Metronidazole:


Pearls and fun nuggets:

Metronidazole could be cancerous 😯 Metronidazole is listed by the U.S. National Toxicology Program (NTP) as reasonably anticipated to be a human carcinogen.[26] Although some of the testing methods have been questioned, oral exposure has been shown to cause cancer in experimental animals and has also demonstrated some mutagenic effects in bacterial cultures.[26][27] The relationship between exposure to metronidazole and human cancer is unclear.[26][28]

2. It’s not too pricey 💲In the United States, it is about US$26 for ten days of treatment.[4

3. It’s frequently used 📈 In 2016, it was the 71st most prescribed medication in the United States, with more than 11 million prescriptions.[12]

4. Metronidazole comes in many forms 🍦 is available by mouth, as a cream, and by injection into a vein.[4]

5. It’s a common antibiotic for pets 🐕 is widely used to treat infections of Giardia in dogs, cats, and other companion animals, although it does not reliably clear infection with this organism and is being supplanted by fenbendazole for this purpose in dogs and cats.[48]

Patient Perspectives

“Was put on Cypro and Flagyl for Diverticulitis. Worked very well. Still have some pain but most of the issues have gone away. I do have some fatigue but that could also be a result of having a major infection. The bottom line is things would be far worse without these antibiotics.”


“Flagyl was prescribed to me after an appendectomy with a leaking appendix. I took 3 doses at home and the side effects started immediately and became more severe with every subsequent dose. I was dizzy to the point of having to hold on to the wall to walk. I had the worst metallic bad taste in my mouth that actually made everything taste horrible (water, juices, food etc). I was extremely nauseous to the point that I started heaving even with liquids. I had severe diarrhea as well, which I am not sure was related to Flagyl or not, but subsided once I was off that medicine. I was changed to Cypro and have been feeling much, much better with that antibiotic. In my case I will NEVER take Flagyl again, based on the severe reaction I’ve experienced”


“My Dr. put me on this metronidazole for ten days because of Diverticulitis. I am a avid walker and because of the side effects such as permanent damage to the nerves in my arms, hands, and feet I am afraid to walk. This medication is doing it’s job but it has made me unable to sleep on a regular base ,muddy stool, and very weak. At sixty six years old I take all the side effects very serious.”

Brandon Simpson, PA-C
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