Major Uses

Metronidazole is an antibiotic and antiparasitic that comes in oral and injection form. It is most commonly used for treating giardia in dogs and cats, as well as for treating parasites such as trichomonas and balantidium coli in small animals. It may also be used for treating enteric and systemic anaerobic infections. Metronidazole is sometimes used in horses to treat anaerobic infections.

Common Precautions

Metronidazole is not to be used in food animals because of FDA restrictions. It should also not be used in animals that are severely debilitated, pregnant, or nursing. It should be used cautiously in animals with hepatic dysfunction or significant liver impairment.

Some negative side effects associated with metronidazole include neurologic disorders, weakness, lethargy, neutropenias, hematuria, hepatotoxicity, anorexia, vomiting, nausea, and diarrhea. Cats specifically tend to suffer from vomiting, inappetence, hepatotoxicity, and central nervous toxicity. Horses may suffer from anorexia, depression, diarrhea, and ataxia.

Metronidazole should not be used in animals with a known allergy or hypersensitivity to the drug. A veterinarian should be contacted immediately if an overdose is suspected. Common symptoms of an overdose caused by metronidazole in dogs and cats are anorexia, vomiting, mydriasis, depression, nystagmus, head-tilt, ataxia, proprioception deficits, joint knuckling, tremors, seizures, disorientation, bradycardia, stiffness, and rigidity.


Metronidazole should be kept at room temperature and stored in a tight, light resistant, childproof container. It should also be protected from light and freezing.


A typical dose of metronidazole used for treatment in dogs and cats is between 15-25 mg/kg every 12-24 hours for up to 7 days. For treating anaerobic infections in horses, a typical dose is between 10-25 mg/kg every 8-12 hours or 3-4 times a day depending on what is being treated. Should a dose be forgotten, it should be administered as soon as possible. Should it almost be time for the next scheduled dose, the missed dose should be skipped and the regularly scheduled dose should be administered. Two doses should never be administered at the same time, as overdose may occur.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.