• Tablets: 125 mg, 250 mg
  • Suspension: compounding pharmacy can make in various strength mg/ml for dosing.


Griseofulvin is a fungistatic which is produced by Penicillium bacteria. It inhibits the synthesis of hyphal cell wall, inhibits mitosis, as well as affecting the synthesis of DNA. It acts against Microsproum, Trichophyton and Epidermophyton, but is not effective against candida or P. orbiculare.

The drug concentrates in skin, hair, nails, fat, muscle and liver. It is metabolized in the liver and excreted in the urine.

Griseofulvin is not recommended for use in pregnant animals.


Used to treat infections caused by dermatophyte fungal infections (i.e., ringworm [tinea]) caused by trichophyton and microsporum) of the skin, hair/fur and nails.

Drug Interactions or Contraindications

  • Blood levels of griseofulvin decreased when used with phenobarbital and other barbiturates.
  • Griseofulvin reduces activity of coumadin and other anticoagulants.

Adverse Reactions

Skin: itching

GI: increased thirst, diarrhea

Blood: granulocytopenia, leukopenia

Dosage Recommendations

Comes in microsize and ultramicrosize. When using the ultramicrosize, dosage should be half the the microsize due to its more complete and rapid absorption.

25 mg/kg, PO, q24hr for 14 days  2


25 mg/kg, PO, q24hr  35


25 mg/kg to 50 mg/kg, PO, q12hr for 14 to 60 days  1


1.5% in DMSO topical for 5 to 7 days  2


  • Treatment may be required for a longer period.
  • Give with food to prevent GI distress.
  • Prevent further reinfection by cleaning disinfecting cage and cage articles.
  • Clip nails to prevent secondary infections.
  • Store drug in closed containers away from light.


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