Griseofulvin

Griseofulvin has been available since 1958 to treat ringworm. It is not effective against yeasts like candida or malasezia.

Griseofulvin has been withdrawn from the market in New Zealand (2002) and in other countries as it has been replaced by more effective and safer antifungal medications.

Griseofulvin comes from mold, Penicillium griseofulvum. It stops the division of fungal cells (that is, it is fungistatic) but does not directly kill them. This means that the treatment should be continued for several weeks or months. For many fungal infections, especially of the nail (tinea unguium), newer medications work better than griseofulvin.

Griseofulvin may still be preferable for ringworm of the head, especially when due to Microsporum canis infection, and is generally well tolerated in children.

Griseofulvin tablets are not very well absorbed from the intestine. They should be taken after a meal or milk drink as fat increases absorption. The drug is transported to the skin by sweat and in a couple of weeks it concentrates on the outer layers of the skin.

Half of the drug is eliminated from the bloodstream in 10 to 20 hours; the rest is eliminated in urine and faeces. This means that the medicine can be taken once a day. Griseofulvin should be continued until the fungal infection has completely disappeared because the drug is rapidly cleared from the skin and hair when it stops

Dose regimen

Adults: 500 mg to 1 g daily.

Children: 10:25 mg per kg of body weight per day.

Tinea pedis, Tinea cruris, tinea manuum, tinea corporis, etc. for 2: 6 weeks.

Ringworm of the head for at least 6: 8 weeks (longer for M. canis).

Ringworm for 12: 18 months until all signs of nail infection disappear.

Side effects

Minor side effects are quite common and include:

• Headaches
• Gastrointestinal upset: nausea, vomiting, heartburn, cramps, flatulence, taste changes, hairy tongue.
• Skin rashes including urticaria, lupus erythematosus and photosensitivity (protect your skin from the sun).
• Urinary disorder: frequency, bedwetting.
• Nervous system disorders: blurred vision, dizziness, depression, nightmares, fatigue.
• Menstrual disorders.
• Liver disorder

Griseofulvin should no taken in pregnancy as there is a slight risk of malformation of the fetus Men should not father children within 6 months of treatment with griseofulvin, as it can damage sperm.

Drug interactions

Griseofulvin may interact with other medications.

Antacids and H2 antagonists should not be taken for 2 hours after griseofulvin otherwise they may stop its absorption.

Griseofulvin interacts with alcohol like disulfiram (Antabuse) and can cause severe nausea and vomiting.

Griseofulvin may cause an increase in the liver. enzyme reducing the concentration of:

• Warfarin (thinning the blood less than required)

• Oral contraceptives (increase the chances of pregnancy)