indication

For the treatment of ringworm infections of the skin, hair, and nails, namely: tinea corporis, tinea pedis, tinea cruris, tinea barbae, cradle cap or other conditions caused by Trichophyton or Microsporum fungi.

pharmacology

Griseofulvin is a mycotoxic metabolic product of Penicillium spp. It was the first available oral agent for the treatment of dermatophytoses and has now been used for more than forty years. Griseofulvin is fungistatic with in vitro activity against various species of Microsporum Epidermophyton, and Trichophyton. It has no effect on bacteria or on other genera of fungi. Following oral administration, griseofulvin is deposited in the keratin precursor cells and has a greater affinity for diseased tissue. The drug is tightly bound to the new keratin which becomes highly resistant to fungal invasions. Once the keratin-Griseofulvin complex reaches the skin site of action, it binds to fungal microtubules (tubulin) thus altering fungal mitosis.

mechanism of action

Griseofulvin is fungistatic, however the exact mechanism by which it inhibits the growth of dermatophytes is not clear. It is thought to inhibit fungal cell mitosis and nuclear acid synthesis. It also binds to and interferes with the function of spindle and cytoplasmic microtubules by binding to alpha and beta tubulin. It binds to keratin in human cells, then once it reaches the fungal site of action, it binds to fungal microtubes thus altering the fungal process of mitosis.

toxicity

Side effects are minor: headaches, gastrointestinal reactions and cutaneous eruptions

biotransformation

Primarily hepatic with major metabolites being 6-methyl-griseofulvin and its glucuronide conjugate.

absorption

Poorly absorbed from GI ranging from 25 to 70% of an oral dose. Absorption is significantly enhanced by administration with or after a fatty meal.

half life

9-21 hours

drug interactions

Acenocoumarol: Griseofulvin may decrease the anticoagulant effect of acenocoumarol.

Acetylsalicylic acid: Griseofulvin may decrease the efficacy of acetylsalicylic acid.

Amobarbital: The barbiturate, amobarbital, decreases the effect of griseofulvin.

Anisindione: Griseofulvin may decrease the anticoagulant effect of anisindione.

Aprobarbital: The barbiturate, aprobarbital, decreases the effect of griseofulvin.

Butabarbital: The barbiturate, butabarbital, decreases the effect of griseofulvin.

Butalbital: The barbiturate, butalbital, decreases the effect of griseofulvin.

Butethal: The barbiturate, butethal, decreases the effect of griseofulvin.

Chlorotrianisene: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, chlorotrianisene.

Clomifene: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, clomifene.

Conjugated Estrogens: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, conjugated estrogens.

Cyclosporine: Griseofulvin decreases the effect of cyclosporine

Dicumarol: Griseofulvin may decrease the anticoagulant effect of dicumarol.

Diethylstilbestrol: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, diethylstilbestrol.

Dihydroquinidine barbiturate: The barbiturate, dihydroquinidine barbiturate, decreases the effect of griseofulvin.

Estradiol: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, estradiol.

Estriol: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, estriol.

Estrone: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, estrone.

Estropipate: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, estropipate.

Ethinyl Estradiol: This product may cause a slight decrease of contraceptive effect

Heptabarbital: The barbiturate, heptabarbital, decreases the effect of griseofulvin.

Hexobarbital: The barbiturate, hexobarbital, decreases the effect of griseofulvin.

Medroxyprogesterone: The enzyme inducer, griseofulvin, may decrease the effect of the hormone, medroxyprogesterone.

Megestrol: The enzyme inducer, griseofulvin, may decrease the effect of the hormone, megestrol.

Mestranol: This product may cause a slight decrease of contraceptive effect

Methohexital: The barbiturate, methohexital, decreases the effect of griseofulvin.

Methylphenobarbital: The barbiturate, methylphenobarbital, decreases the effect of griseofulvin.

Norethindrone: This product may cause a slight decrease of contraceptive effect

Pentobarbital: The barbiturate, pentobarbital, decreases the effect of griseofulvin.

Phenobarbital: The barbiturate, phenobarbital, decreases the effect of griseofulvin.

Primidone: The barbiturate, primidone, decreases the effect of griseofulvin.

Quinestrol: The enzyme inducer, griseofulvin, decreases the effect of the hormone agent, quinestrol.

Quinidine barbiturate: The barbiturate, quinidine barbiturate, decreases the effect of griseofulvin.

Secobarbital: The barbiturate, secobarbital, decreases the effect of griseofulvin.

Talbutal: The barbiturate, talbutal, decreases the effect of griseofulvin.

Warfarin: Griseofulvin may decrease the anticoagulant effect of warfarin.