Griseofulvin Powder (microsize) is available in 15-gram packets each containing 2.5 grams griseofulvin (microsize). Griseofulvin Powder (microsize) is an orally effective antifungal antibiotic specifically active against superficial fungi which cause tinea (ringworm) of the skin and hair. This microsize form of griseofulvin differs from regular Griseofulvin Powder products in that its finer particle size results in a much greater surface area for absorption. An increased blood level has been obtained in experimental studies in man using fine particle size griseofulvin, indicating better absorption and a greater amount of the drug available for fungistatic action in the skin and hair.
Cases of ringworm in horses caused by T.equinum and M. gypseum should be treated with the Griseofulvin Powder (microsize) product for not less than 10 days. Responsive cases may show clinical signs of recovery in 5 to 7 days after griseofulvin therapy is initiated. In responsive cases, treatment should be continued until all infected areas are negative by appropriate culture.
If cases do not respond to therapy in 3 weeks, it is recommended that the diagnosis be reevaluated.
The powder may be given on a small amount of feed or in a drench
WARNING: Do not use in horses intended for human consumption.
The safety and efficacy of prophylactic use of griseofulvin have not been established. This drug should not be used to treat minor or trivial infections.
Safety of griseofulvin for use in pregnant animals hat not been established. It has been reported in the Soviet literature (N.N. Slonitskaya; Teratogenic Effect of Griseofulvin-Forte on the Rat Fetus/Antibiotiki 13(1): 44-48, 1969) that a griseofulvin preparation was found to be embryotoxic and teratogenic on oral administration to pregnant Wistar rats. Also, pups and kittens with either cleft palates or other abnormalities have been reported in litters of bitches and queens treated with griseofulvin during gestation.
PRECAUTIONS: Patients on prolonged therapy with any potent medication should be under close observation. Periodic monitoring of organ system function, including renal, hepatic, and hemopoietic, should be done.
This antibiotic is derived from a species of Penicillium griseofulvum. Some known penicillin-sensitive humans have been treated with griseofulvin without difficulty. In veterinary medicine, the drug has no allergenic properties; however, considerably more experience in this area must be obtained before definite conclusions may be drawn.
Griseofulvin administered to animals intraperitoneally or intravenously in massive doses will produce damage to the seminal epithelium; however, no such effects have been observed following oral administration of usual clinical doses to dogs and cats.
Studies to date indicate that the usual clinical doses of griseofulvin administered orally do not affect spermatogenesis. More evidence is needed, but it appears likely that such effects noted are related to the massive doses administered by the parenteral routes. The effects of griseofulvin on stallion spermatogenesis are not known.
SIDE EFFECTS: Close observation of human and animal patients receiving therapeutic doses thus far reveals no effect on body weight, fasting blood sugar, blood electrolytes, total or differential counts, thymol turbidity tests, urinalyses, or sternal marrow counts.
In the human, heartburn, nausea, epigastric discomfort, and diarrhea have occasionally been reported, In a few instances, urticaria or drug rashes have developed, and in these instances, the drug should be withdrawn. Generally, the incidence of side effects has been quite low, and the drug seems to be well tolerated when given orally.
The veterinarian is alerted to the following griseofulvin associated side effects which have been reported in either human or veterinary literature: irritability, dizziness, memory loss, visual disturbances, antagonism to barbiturates and other drugs metabolized by the liver, such as warfarin-type anticoagulants.
It has also been reported that griseofulvin effects disturbances in porphyrin metabolism, the formation of hepatomata and carcinogenicity with methylcholanthrene; also higher fat diet increases absorption of the antibiotic.