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Drug Info

  • Drug Name: Metronidazole for Dogs and Cats
  • Common Name: Flagyl®, Metizol®, Protostat®, Metrogel®
  • Drug Type: Antibiotic, antiprotozoal
  • Used For: Prevention and treatment of bacterial and parasitic infections
  • Species: Dogs, Cats
  • Administered: Tablet, Oral liquid, Injectable
  • How Dispensed: Prescription only
  • FDA Approved: No



What Is Metronidazole?

Metronidazole (also known as Flagyl) is used primarily as an anti-diarrheal medication for dogs and cats. It is effective against certain protozoal infections including Giardia, Trichomonas, and Balantidium coli as well as anaerobic bacterial pathogens. Metronidazole may also be prescribed to relieve inflammation of the intestinal tract. Because the drug can penetrate the blood-brain barrier and bone, it is sometimes used to treat infections of the central nervous system, bones, and teeth. 


How Metronidazole Works

Metronidazole’s mechanism of action is not fully understood. It may disrupt the ability of some microorganisms to make new genetic material. Its anti-inflammatory action within the gastrointestinal tract may be related to suppression of some parts of the immune system.

Storage Information

Keep the oral, liquid form of metronidazole refrigerated and shake well before use. Tablets and capsules are to be kept in a tightly sealed container at room temperature and protected from heat and light.

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. Higher doses may be given once daily, while lower doses are generally given twice daily. Always follow the specific dosing instructions provided on the label of your pet’s medication and contact your veterinarian with any questions or concerns.

What to Do If You Miss a Dose of Metronidazole 

Give the dose as soon as possible. If it is almost time for the next dose, skip the missed dose, and continue with the regular schedule. Do not give your pet two doses at once.


Side Effects of Metronidazole 

Because metronidazole crosses the blood-brain barrier, neurologic side effects are possible with the use of this drug. Typically these occur when pets ingest more than the recommended dose or when they are on long-term therapy, particularly if they are debilitated or suffer from liver dysfunction. Signs of neurologic side effects from metronidazole include:

  • Depression and disorientation
  • Unsteadiness when standing or walking
  • Unusual eye movements
  • Head tilt
  • Tremors
  • Seizures
  • Stiffness

Other possible side effects of metronidazole use in dogs and cats include:

  • Allergic reaction (labored breathing, hives, etc.)
  • Drooling and gagging (the drug is very bitter)
  • Vomiting
  • Loss of appetite
  • Diarrhea
  • Lethargy
  • Blood in the urine, or dark urine
  • Liver damage


Drugs That React with Metronidazole

  • Cimitidine
  • Cyclosporine
  • Warfarin
  • 5-Fluorouracil
  • Phenytoin
  • Phenobarbital 



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