Metronidazole (Flagyl®) for Dogs and Cats


Overview of Metronidazole for Dogs and Cats

  • Metronidazole, a common prescription drug known as Flagyl®, Metric 21®, and Protostat®, is a synthetic antibiotic and antiprotozoal used to treat and prevent bacterial infections and treat certain parasitic infections in dogs and cats.
  • This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.
  • Metronidazole is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • Brand Names and Other Names of Metronidazole

  • This drug is registered for use in humans only.
  • Human formulations: Flagyl® (Searle), Metric 21® (Fielding), Protostat® (Ortho), Metro® (McGaw). Metronidazole is supplied by numerous drug companies with a variety of trade names and various generic formulations.
  • Veterinary formulations: None
  • Uses of Metronidazole for Dogs and Cats

  • Metronidazole is prescribed to treat or control infections caused by susceptible bacteria and parasites.
  • Metronidazole is effective against infections caused by Giardia, Trichomonas and Balantidium coli.
  • Metronidazole is not effective against viruses.
  • Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, metronidazole can cause side effects in some animals.
  • Metronidazole should not be used in animals with known hypersensitivity or allergy to the drug.
  • Metronidazole should be used with caution in severely debilitated or pregnant animals.
  • Metronidazole should be avoided in animals with liver disease.
  • Metronidazole may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with metronidazole. Such drugs include phenobarbital and cimetidine.
  • Adverse effects associated with metronidazole include neurologic disorders, lethargy, weakness, liver disease and lack of appetite.
  • Prolonged use or overdose can result in significant neurologic signs including nystagmus, ataxia, head tilt, disorientation, tremors, seizures and rigidity.

    How Metronidazole Is Supplied

  • Metronidazole is available in 250 mg and 500 mg tablets and 375 mg capsules.
  • Metronidazole is available in 500 mg/vial and 5 mg/ml injectable solutions.
  • Dosing Information of Metronidazole for Dogs and Cats

  • Medication should never be administered without first consulting your veterinarian.
  • The typical dose of metronidazole ranges from 5 to 30 mg per pound (10 to 60 mg per kilogram) one to four times a day in both dogs and cats. 
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.
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    Antibiotics & Antimicrobial Drugs



    Dentistry & Oral Cavity diseases
    Gastroenterology & Digestive diseases
    Orthopedics & Musculo-Skeletal diseases
    Multiple organ systems can be affected