Metronidazole for cats

Metronidazole is a medication with both antibiotic and antiprotozoal properties used to treat bacterial infections, inflammatory bowel disease and giardiasis. Although widely prescribed for animals, it's not officially approved for veterinarian use.

Metronidazole destroys bacteria by interfering with their DNA function. Because it's only effective against bacteria that survive without oxygen, it's usually combined with other antibiotics to treat cats suffering from multiple infections. For giardiasis, however, metronidazole is effective on its own.

Uses of Metronidazole in Cats

In addition to treating giardiasis, says veterinarian Barbara Forney, metronidazole can kill trichomonas, entamoeba and balantidium protozoal infections. Because it regulates immune system response, metronidazole helps relieve inflammatory bowel disease, especially when combined with corticosteroids.

Corticosteroids and metronidazole are also effective in fighting feline gum disease (gingivitis). Metronidazole cream can fight your cat's skin infections.

Types of Metronidazole

Metronidazole is available as a liquid suspension, tablets and a topical cream. Because of its extremely bitter taste, however, your pet may refuse to take the tablet.

One way to make the metronidazole tablets taste better to your cat is to order them from a compounding pharmacy that can prepare it as a flavoured tablet. Getting it from such a pharmacy will let you tailor the dosage of each tablet to your vet's recommendation. These pharmacies can also prepare metronidazole suspensions and creams.

A list of compounding pharmacies that provide veterinary medicines is available at the Veterinary Partners website. (See the Resources section.)

Administering Metronidazole

Because metronidazole isn't approved for veterinary use, its manufacturers haven't established a dose for cats. Your vet will prescribe a dose dependent on your pet's weight and condition. The U.S. Pharmocoepial Convention says a typical dose for cats 15mg/0.998kg. of weight given every 12 hours.

Don't let your cat chew the metronidazole tablets or he may begin to drool and paw his mouth. Giving the oral suspension with food may help your cat tolerate the medication better.

Side Effects

Although most metroniadozle side effects occur only at extremely high doses, some animals have had adverse reactions when receiving doses of 30 mg/9.98kg. of weight.

Side effects requiring veterinary attention include seizures, muscle weakness and liver disease resulting in jaundice (yellowing) of the eyes, gums and skin. Severe side effects, says Dr. Forney, usually surface after your cat has been taking the medication for between 1 week and 12 days, and can take up to 2 weeks to subside once the metronidazole is discontinued.

Less serious side effects that often clear up on their own include loss of appetite vomiting and low white blood cell count. If your cat stops eating entirely or continues to vomit frequently while taking metronidazole, stop using it and have your vet check her out.

This medication will give your cat's urine a reddish colour, but that's normal and will stop once she's no longer taking it.


While metronidazole has proven effective in treating giardiasis-related diarrhoea and eliminating the infective cysts that cats pass in their stool, it may not kill all the organisms. Removing giardia from your pet's environment is the only way to prevent reinfestation.