Dogs and Cats. Metronidazole is used to treat protozoal infections in dogs and cats including Giardia, Entamoeba, Trichomonas, and Balantidium. It also is used to treat anaerobic bacterial infections. Metronidazole oral tablets are available as both generic and brand-name drugs. Brand names: Flagyl (immediate-release), Flagyl ER (extended-release). The 200mg tablets are supplied in packs of 14, 21 and 250 and the 400mg tablets are supplied in packs of 14, 21 and 100. The active ingredient, metronidazole, is an antibacterial agent used to treat infections. Metronidazole Dosage for Dogs and Cats The dosage for metronidazole in dogs and cats varies depending on its intended use and the specifics of a patient’s case. A dose range of between 5 and 25 mg/lb given by mouth is typical. Metronidazole tablets should be swallowed, without chewing, with half a glassful of water during or after meals. Prophylaxis against anaerobic infection: Chiefly in the context of abdominal (especially colorectal) and gynaecological surgery. Metronidazole 200mg and 400mg Tablets Read all of this leaflet carefully before you start taking this medicine. • Keep this leaflet. You may need to read it again. How to use Metronidazole. Take this medication by mouth as directed by your doctor. To prevent stomach upset, take this medication with food or a full glass of water or milk. Metronidazole is a synthetic nitroimidazole compound used with increasing frequency in small animal practice. It is commonly prescribed in the treatment of inflammatory bowel disease, gastritis associated with helicobacter, giardiasis and empirical treatment of diarhea. The proper dosage of metronidazole for dogs depends on which condition is being treated. You should always rely on your veterinarian to give you the proper dosage for your dog. Metronidazole Directions: Metronidazole is a prescription antibiotic used in dogs and cats to treat various conditions such as inflammatory bowel disease, nonspecific diarrhea disorders, infections caused by Giardia, and periodontal disease.