Metronidazole (Flagyl®)

Metronidazole (Flagyl®)


Metronidazole has several uses in veterinary medicine.  It is effective against Giardia parasites.  It is employed in the treatment of many forms of diarrhea, including diarrhea caused by colitis and inflammatory bowel disease.   It aids in the treatment of certain liver disorders.  Metronidazole is an antibiotic that may be used in the treatment of certain types of bacterial infections.


Metronidazole is most commonly supplied as a pill.  Liquid formulations are available. Compounding pharmacies are able to prepare palatable suspensions of the medication. Veterinarians may administer metronidazole by injection to hospitalized patients.

Side Effects

Many pets exhibit an adverse reaction to the flavor of metronidazole when it is administered as a pill.  The pills may be supplied in inert gelatin capsules to prevent pets from tasting them.

Metronidazole is often prescribed to treat gastrointestinal upset, and it often is effective in this capacity.  However, in rare cases it may trigger or exacerbate gastrointestinal upset as a side effect.

Some animals may experience lethargy, weakness, or neurological problems while taking metronidazole.  The medicine should be discontinued immediately if any of these side effects occur.


The effectiveness of metronidazole is monitored through response to therapy, such as resolution of diarrhea.

Pets that take metronidazole to treat inflammatory bowel disease or liver disease may require long-term or repeated courses of the medication.  Periodic organ function tests (blood tests) should be performed on any animal that takes metronidazole regularly.

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The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.