White to pale cream crystalline powder, odourless or nearly odourless but bitter tasting. (B263, W324)

• Very slightly soluble. (B263)

• <0.1 g/100 mL at 21°C. (W324)

• Sparingly soluble in alcohol. (B263)

• In susceptible fungi, arrests the metaphase of cell division by disrupting the structure of the mitotic spindle. (B263)

• Store below 40°C, preferably at room temperature (15-30°C), in a tight, light-resistant container. (B263)

Associated Techniques

• Active against Trichophyton spp., Microsporum spp. and Epidermophyton spp. (B263)
• Following administration, griseofulvin is deposited in the keratin precursor cells and becomes concentrated in the stratum corneum of the skin, hair and nails, thus preventing invasion of newly formed cells by fungus. (B201.1.w1)

• Dogs, cats: for the treatment of dermatophytic fungal infections of the skin, hair and claws. (B263)
• Treatment of dermatophyte infections. (B201.1.w1
• Horses: for the treatment of Trichophytes equinum and Microsporum gypseum ringworm. (B263)
• In ruminants and laboratory animals for the treatment of dermatophytic fungal infections. (B263)

• Only protects new hair and nail growth. (B263)
• Not clinically useful against pathogenic fungi other than the dermatophytes. (B263)
• No antibacterial activity. (B263)

• Following oral administration, absorption of microsize form 25-70%. (B263)
  • absorption is enhanced by dietary fat. (B201.1.w1, B263)
• Following oral administration of ultramicrosize form absorption may approach 100% (generally about 1.5 times as well absorbed as the microsize form for a given individual). (B263)

• Concentrated in skin, hair, nails, fat. skeletal muscles and liver.(B263)
• Reaches stratum corneum within four hours of administration. (B263)

• Metabolised in the liver (B201.1.w1) via oxidative demethylation and glucuronidation to inactive 6-desmethylgriseofulvin. (B263)
  • The known greater tendency to adverse effects in cats may be due to slower formation of glucuronide conjugates and therefore slower metabolism of the drug. (B263)
• Excretion of unchanged griseofulvin in urine is very low: less than 1% of the original dose. (B263)

• Human: half-life 9-24 hours. (B263)
• Dog: serum half-life of 47 minutes reported. (B263)

• Blood concentration may be decreased if given concurrently with barbiturates such as phenobarbital, probably due to induction of hepatic microsomal enzymes; an adjustment may be required in the dose of griseofulvin. (B263)
• Griseofulvin may reduce the anticoagulant activity of coumarin anticoagulants such as warfarin such that the dose of the anticoagulant may require adjustment. (B263)
• The effects of alcohol may be potentiated by griseofulvin. (B263)

• Oral pastes, tablets, granules and suspensions are available. (B201.1.w1)

Use of Drugs (Medication):

• Before administration of any pharmaceutical product the manufacturer's datasheet must be consulted regarding operator safety, relevant withdrawal times etc.
• Many drugs are not registered for use in particular species and additional care should be taken in their use, with proper regard for possible toxic effects. 
• Consideration should be given to relevant legislation regarding the use of drugs.
• In the UK, guidelines regarding the use of drugs are set out in the Royal College of Veterinary Surgeons' Guide to Professional Conduct 2000: (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Choice of Medicinal Products).

• Oral administration. (B201.1.w1)
• Treatment for three to four weeks is commonly required and up to twelve weeks of administration may be necessary in some cases. (B201.1.w1)
• Higher doses may be required in dogs and cats than the usual dose, e.g. 40-50 mg/kg daily may be needed. (B201.1.w1)

Dogs: 

• Give after a fatty meal or after giving corn oil. Microsize, 25-50 mg/kg orally every 12 hours for 42-56 days or ultramicrosize 5-10 mg/kg orally once daily for 42 days. Give for at least two weeks after signs resolve. Note: longer treatment may be required  with Trichophyton infections than with Microsporum infections. With nail infections, at least five months of treatment is required. (B263)
• Or Microsize 50 mg/kg orally once daily with a fatty meal, together with topical therapy. The dose can be doubled in resistant cases. If GIT distress occurs, divide the dose, giving twice daily with food. Continue for two weeks after clinical cure and until two or three weekly cultures are negative (start cultures after the first four weeks of treatment). (B263)

• Dogs 15-20 mg/kg daily orally, absorption is enhanced by giving with a fatty meal; treatment for 3-4 weeks and often even up to 12 weeks may be required. The usual dose may not be effective; doses of up to 40-50 mg/kg daily may be required. (B373.1.w1)

Bears (Ursidae - Bears (Family)):

• In general: "Domestic dog drugs and dosages are used to treat bears." (B336.51.w51)
• Microsporum canis infection in bears has been treated with 500 mg/ day oral griseofulvin in the diet for 30 to 60 days. (B16.9.w9, B64.26.w5)
• Griseofulvin (microcrystalline), orally, at 500 mg per day for each of two Helarctos malayanus - Sun bears, approximate bodyweight 45 kg each; 250 mg/day appeared to be ineffective. (J4.155.w5) 
• For Ursus americanus - American black bear cubs, griseofulvin (Fulvicin, Schering) microsize, 10 mg/kg orally twice daily for 4-6 weeks, or for at least 21 days and continuing for one to two weeks after clinical signs have ceased. Additionally, topical treatment (on affected areas or the whole bear) with lyme sulphur solution. (B338.23.w23)
  • Note: griseofulvin can cause low leucocyte count. Check the blood count every two to three weeks during treatment, or if the bear shows any adverse clinical signs. (B338.23.w23)

• 50 mg/kg daily, orally. For skin and deep mycoses; long term therapy. (B22.27.w3)
• 30-50 mg/kg orally once daily. For treatment of ringworm. Continue therapy for at least four weeks. (B284.6.w6)
• 25-30 mg/kg orally once daily (Grisovin, Coopers Pitman-Moore). (D107)
• 0.1ml Fulcin oral suspension (Coopers) orally once daily for three weeks. Easier for small hogs. (D107)
• 25 mg/kg twice daily or 50 mg/kg once daily, orally. (D107)

Atelerix albiventris - Four-toed hedgehog:

• 50 mg/kg (microsize) oral per day in divided doses every 8-12 hours. Fungal infections. (J204.59.w1)

• Microsize formulation: 25 mg/kg orally, every 12 hours. (B267)
• Microsize formulation: 50 mg/kg orally, every 24 hours. (B267)
• For skin and deep mycoses; long term therapy required. (B267)
• 50 mg/kg oral daily for six to eight weeks. (B150.w1)

Lagomorphs - Oryctolagus cuniculus domesticus - Domestic rabbit:

• 25 mg/kg orally once daily for four weeks. (B373.Guide.w41)
• 12 mg/kg orally every 12 hours for 30 - 45 days. (B548.w8)
  • For the treatment of advanced cases of dermatophytosis. (B548.w8)
  • Note: "decrease dose by 50% with ultramicrosize form (GrisPEG, Allergan Herbert), which has better absorption." (B548.w8)
• 25 mg/kg orally every 24 hors for 30 - 45 days. (B548.w8)
• 25 mg/kg orally daily for at least two weeks. Treatment of ringworm. (B600.4.w4)
• 25 mg/kg orally daily for 14 to 45 days. (B601.15.w15)
• Note: "highly teratogenic, do not use in breeding does." (B601.15.w15)
• 12.5 mg/kg orally every 12 hours. (B602.41.w41)

• Contraindicated in individuals known to be sensitive to griseofulvin. (B263)
• Contraindicated in individuals with hepatic impairment. (B201.1.w1, B263)
• In kittens, careful monitoring is required as they may be very sensitive to the adverse effects. (B263)
• In cats, testing for FIV is suggested prior to treatment due to the possible neutropaenic or panleucopaenic effects of the drug. (B263)
• Contraindicated during pregnancy. (B201.1.w1, B263)
  • May be teratogenic; should not be given to pregnant animals. (B373.1.w1)

• Anorexia, vomiting, diarrhoea, anaemia, neutropaenia, leucopaenia, depression, ataxia, hepatotoxicity, dermatitis/photosensitivity are all possible side effects. (B263)
• At normal doses side effects other than gastro-intestinal signs are uncommon. (B263)
• Cats, especially kittens, may be more prone than are other species to adverse effects such as bone marrow depression. (B263)
• Hepatotoxicity may result from high doses, particularly in cats. (B201.1.w1)

• No specific data. gut emptying, charcoal and administration of cathartics may be useful for significant overdose. (B263)

• No data. (B263)

• Horses: no apparent ill effects following oral administration of 100 mg/kg daily for 20 days. (B263)

• May inhibit spermatogenesis. (B263)

• May be teratogenic. (B201.1.w1, B373.1.w1)
• Cats: known teratogen. Doses of 35 mg/kg administered during the first trimester of pregnancy may cause cleft palate and other skeletal and brain abnormalities in kittens. (B263)

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