Metronidazole for Dogs With Diarrhea

Updated November 21, 2016

Diarrhoea in dogs has many possible causes. A veterinarian may prescribe metronidazole (brand name Flagyl) for the treatment of diarrhoea caused by anaerobic bacteria or protozoa.

What Is Metronidazole?

Metronidazole is a synthetic antibacterial and antiprotozoal antibiotic.


Metronidazole is administered in tablet, capsule or injectable form. Because it has a bitter taste, pills should not be crushed. Metronidazole should be administered to your dog along with food.

How Metronidazole Works

According to "The Merck Veterinary Manual, Ninth Edition," metronidazole is readily absorbable from the gastrointestinal tract. It is thought to impair DNA function of the bacterial or protozoal organism. The drug is metabolised by the liver.

Adjunct Treatment

Because it specifically treats anaerobic bacteria, metronidazole is often given in combination with other antibiotics. This is especially the case when the dog's diarrhoea is of unknown origin.

Side Effects

Reported side effects in dogs taking metronidazole include excessive salivation, nausea and decreased appetite.


Metronidazole should not be given to pregnant dogs.

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