Therapeutic Class: Antifungal
Species: Horses
May Be Prescribed For: Ringworm
Basic Information
Griseofulvin is an antifungal agent which, when taken orally, is active against the superficial fungi that cause ringworm of the skin, hair and claws. Griseofulvin has activity against Trichophyton, Microsporum and Epidermophyton. It has no antibacterial activity and is not effective against other fungi. It is approved for use in dogs, cats and horses. Adverse effects include anemia, anorexia, depression, vomiting and diarrhea. Safety in pregnant animals has not been established.
Griseofulvin should be given with food to enhance absorption. Griseofulvin enhances cytochrome P-450 enzymes and may cause an increased metabolism and clearance of concurrently administered drugs. The FDA label use of griseofulvin is to treat ringworm infections caused by trichophyton equinum and microsporum gypseum. The usual dose for a 1,000 pound horse is 2.5 grams once daily by mouth for a minimum of 10 days.
Off-Label Use
In my practice, most of the griseofulvin use is off-label. Dr. Edwin Churchill observed in a clinical setting that griseofulvin is a useful adjunct therapy to antibiotics when treating lower airway disease and the accompanying mucous. A single bolus ten-day dose of 25 grams is administered by stomach tube or paste when the antibiotics are initiated.
Practice Tip
To facilitate the suspension and administration of the griseofulvin powder, place the griseofulvin powder in a pitcher. Add five to six capfuls of docusate sodium liquid 50mg/5ml and mix with the powder to make a paste before adding water. The docusate sodium is a surfactant and helps to wet the powders making mixing with water easier.