Metronidazole Trade and Other Names
Flagyl; many brands available
Drug Class
Antibacterial, antiparasitic, antiprotozoal
Mechanism of Action and Clinical Use
Disrupts DNA in organism via reaction with intracellular metabolite. Action is specific for anaerobic bacteria and protozoa. Resistance is rare. Active against some protozoa, including Giardia organisms; however, other drugs such as fenbendazole have been used for Giardia infection.
Adverse Effects
Most severe adverse effect is dose-related CNS toxicity. High doses have caused lethargy, CNS depression, ataxia, vomiting, and weakness. Metronidazole may be mutagenic.
Contraindications, Precautions, and Drug Interactions
Fetal abnormalities have not been demostrated in animals with recommended doses, but use with caution during pregnancy.
Instructions for Use
Metronidazole is one of the most commonly used drugs for anaerobic infections. It is effective for giardiasis; other drugs used for Giardia infection include albendazole, fenbendazole, and quinacrine. Maximum dose that should be administered is 50-65 mg/kg,q24h, in any species. Tablets have been broken or crushed for oral administration to cats; however, cats find these unpalatable.
Small Animal Dosage Information
Anaerobic Infection:
Dogs: 15 mg/kg,q12h, PO; or 12 mg/kg, q8h, PO.
Cats: 10-25 mg/kg, q24h, PO.
Giardia Infection:
Dogs: 12-15 mg/kg,q12h, PO, x 8 days.
Cats: 17 mg/kg (1/3 tablet/cat), q24h, PO, x 8 days
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