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griz-e-o-FUL-vin - Pronunciation guide

Brand Names

  • Fulvicin® U/F Powder
  • Norofulvin Equine Paste


Rx symbolGriseofulvin is a fungistatic antibiotic that is effective against the fungi that cause ringworm and other fungal skin infections.  It works by disrupting fungal reproduction and is effective in protecting new skin or hair growth from infection.  It will not clear infection from hair or skin cells that are already involved.  Griseofulvin is a systemic treatment and is more costly than drugs used in topical treatments.


Griseofulvin is used to treat fungal infections caused by dermatophytes that thrive in warm, moist, dirty environments and invade the horse's superficial skin layers through minor abrasions or injuries.  Infection causes itching, hair loss, scales, and crusts that often take a circular pattern, giving the infection the name "ringworm." Griseofulvin is a systemic treatment and is most often used in selected cases of animals with underlying immune problems or severe infections.

Dosage and Administration

Prescription medicationGriseofulvin
Method Dosage
(click row for calculator)
Concentration Period Duration
Oral 2.5-5 mg/lb 2500 mg/packet Daily Not less than 10 days


  • Federal law restricts this drug to use by or on the order of a licensed veterinarian.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

Few side effects have been reported from griseofulvin use in horses.  In small animals, griseofulvin can cause gastrointestinal upset.


Griseofulvin is metabolized by the liver and should not be used in horses with decreased liver function.

Griseofulvin has been demonstrated to cause fetal malformations in other species and should not be used with pregnant mares or breeding stallions.

Griseofulvin is FDA approved and is a prescription drug.  Federal law restricts this drug to use by or on the lawful written or oral order of a licensed veterinarian.

Griseofulvin is prohibited in any drug-free competition.  The individual regulatory group should be consulted as to its policies regarding use of the drug and rules for therapeutic use.


Griseofulvin may reduce the activity of oral anticoagulants, such as warfarin.


Horses have been given large doses in experimental studies without signs of toxicity.


Griseofulvin PowderGriseofulvin Powder

Norofulvin GranulesNorofulvin Granules



About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.