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Is my dog's Metronidazole causing diarrhea or other side effects?

Updated on September 23rd, 2025

Pet's info: Dog | German Shepherd | Male | unneutered | 8 years old | 108 lbs

Dehydration, diarrhea. No worms found, bacteria infection. Metronidazole prescribed, broad spectrum wormer.. Dog won't eat dry food wetted down but does eat canned. Dr said this drug can cause diarrhea but he already had it so you may not see improvement yet.. Continue meds. This drug can cause unbalance and grogginess. She wasn't teal thrilled he threw up yesterday but that's also a possible side effect. Absolutely no pepto but a pepcid is OK..is any of this true?

3 Answers

Most Helpful Answer

Stacey Anstaett, DVM

Answered By Stacey Anstaett, DVM

Veterinarian

Published on July 6th, 2018

Sorry Jake is having problems. Metronidazole is often used to treat diarrhea in dogs. It is not common for metronidazole to cause vomiting. However, the underlying CAUSE of the diarrhea is usually some form of gastroenteritis which is inflammation of the stomach and intestine. Gastroenteritis often includes vomiting and can occur for many reasons including:
bacterial imbalance,
viral infections such as parvovirus (Jake is too old for this to be a concern)
ingesting non-food items such as trash or mulch
inflammatory bowel disease
cancer in the GI tract
intestinal parasites

At higher doses, metronidazole can cause "grogginess" or an unsteady gait. If he is showing those signs, discontinue the metronidazole.

Correct, I would hold off on Pepto, but Pepcid AC is fine.

I hope I've answered your questions, and I apologize that we did not get to your question sooner. Please feel free to post again if you still have questions or concerns with Jake.

Thanks for asking Petco Pet Education Center, formerly Petcoach!


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Related Answers from Veterinarians

  • Answered By Sara Farmer, DVM

    Veterinarian

    Published on July 5th, 2018

    I wouldn't expect to see vomiting from metronidazole, it is more likely that whatever has cause his diarrhea is also the cause of the vomiting. Lethargy is not a common side effect either. Although it sounds like Jake is improving overall, I would recommend seeing your veterinarian if he vomits again since it is possible that there is something more serious going on. Your vet might want to run some tests like blood work or abdominal x-rays if the vomiting continues.

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    1Pet Parents found this answer helpful

  • Answered By Maria DVM

    Veterinarian

    Published on July 9th, 2018

    Metronidazole doesn't typically cause diarrhea but not all medications ready the book. I would recommend making sure Romeo is on a bland diet. I would also recommend if Romeo is still having diarrhea and the bland diet is not helping then I would bring him back to the veterinarian to discuss blood work and a fecal culture. Thank you for using Petco Pet Education Center, formerly Petcoach.

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    3Pet Parents found this answer helpful

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