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Griseofulvin: Antifungal Ringworm Treatment for Dogs, Cats, Horses

Published on September 10, 2024
Updated on November 5, 2025
Reviewed by Petco's Veterinarian Team
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Griseofulvin is an antifungal used to treat ringworm infection in dogs, cats, and horses.

Summary

Used For:

Treatment of dermatophyte fungal infections (ringworm), but use has fallen out of favor due to side effects, and availability of effective antifungal therapy with safer drugs such as itraconazole and terbinafine

Brands:

Fulvicin, Gris-PEG

Species:

Dogs, cats and horses

Drug type:

Antifungal

Prescription required:

Yes

Pregnancy and lactation:

Do not use in pregnant or lactating animals as griseofulvin is a potent teratogen. Pregnant women should avoid handling this drug.

Side effects:

Lack of appetite, vomiting, diarrhea, depression or weakness, bone marrow suppression causing neutropenia, especially in cats infected with feline leukemia or feline immunodeficiency viruses. Kittens are more susceptible to side effects.

FDA Approved:

Yes

General description

Griseofulvin has been used in pets to help clear dermatophyte infections, often in conjunction with topical treatments. Use has fallen out of favor due to availability of safer effective medications. Griseofulvin can be toxic and should be used as directed to avoid any side effects. Do not administer to pregnant animals as this drug can be teratogenic. Pregnant women should wear gloves to administer. Avoid use in cats infected with FeLV/FIV.

Uses

Ringworm (dermatophyte) infection; however, griseofulvin use is falling out of favor as more effective anti-fungal medications with fewer side effects such as terbinafine and itraconazole are now available.

How it works

Griseofulvin prevents fungal organisms from replicating.

Dosage

Dogs and Cats: 5-10 milligrams per kilogram ultramicrosize griseofulvin given orally once daily; 25mg/kg day microsize griseofulvin orally once a day with a high fat meal

Forms

125 and 250 mg tablets of ultramicrosize griseofulvin are available; 250 and 500 mg microsize tablets; 125mg/5ml liquid oral suspension; veterinary labeled tablets are not available commercially at this time .

Storage information & handling

Tablets should be stored in a cool, dry place.

What results can I expect?

It may take several weeks to see an improvement in skin lesions due to ringworm infection. Treatment should continue beyond the resolution of the lesions.

Missed Dosage

Consult your veterinarian if a dose is missed. This medication can be easily overdosed.

Overdose / acute toxicity

Overdose is possible, and the normal side effects are more severe with overdose.

Side effects

May be more likely in kittens and include:

  • Lack of appetite
  • Vomiting
  • Diarrhea
  • Depression
  • Weakness

Contraindications

Do not use in:

  • Pets with compromised liver or kidney function
  • Pregnant or lactating animals
  • Cats with FeLV/FIV infection are more likely to develop bone marrow suppression causing neutropenia

Drug interactions

Do not use with phenobarbital, cyclosporine or estrogen-containing medications.

Precaution

Do not use in pregnant or lactating animals. Pregnant women should avoid handling this drug due to teratogenicity. Monitor CBC q 3 weeks during use.

Laboratory considerations

There are no known laboratory considerations when using griseofulvin.

Sources

VIN Veterinary Drug Handbook

Disclaimer
The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.

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