Griseofulvin has been withdrawn from the market in New Zealand (2002) and other countries, as it has been superceded by more effective and safer antifungal drugs.
Griseofulvin comes from the mould, Penicillium griseofulvum. It stops fungal cells dividing (i.e. it is fungistatic) but does not kill them outright. This means treatment needs to be continued for several weeks or months. For many fungal infections, especially of the nail (tinea unguium), newer drugs work better than griseofulvin.
Griseofulvin may still be preferable for tinea capitis, especially when due to Microsporum canis infection, and is generally well tolerated in children.
Griseofulvin tablets are not very well absorbed from the gut. They should be taken after a meal or drink of milk as fat increases the absorption. The medication is carried into the skin by sweat and within a couple of weeks is concentrated in the outer skin layers.
Half the medication is cleared from the blood stream in 10 to 20 hours; the rest is eliminated in urine and faeces. This means the medication can be taken once daily. Griseofulvin should be continued until the fungal infection has completely gone because the medication is quickly cleared from skin and hair when it is stopped.
Adults: 500 mg to 1 g daily.
Children: 10: 25 mg per kg body weight per day.
Tinea capitis for at least 6: 8 weeks (longer for M canis).
Tinea unguium for 12: 18 months until all signs of nail infection have gone.
Minor side effects are quite common and include:
- Gastrointestinal upset: nausea, vomiting, heartburn, cramps, flatulence, taste disturbance, furred tongue.
- Rashes including urticaria, lupus erythematosus and photosensitivity (protect your skin from the sun).
- Urinary disturbance: frequency, bed wetting.
- Nervous system disturbance: Blurred vision, dizziness, depression, nightmares, fatigue.
- Menstrual disturbance.
- Liver disturbance.
Griseofulvin should not be taken in pregnancy as there is a slight risk of malformation of the fetus. Males should not father children within 6 months of treatment with griseofulvin as it may damage sperm cells.
Griseofulvin can interact with other medications.
Antacids and H2 antagonists should not be taken for 2 hours after griseofulvin because they might otherwise stop its absorption.
Griseofulvin interacts with alcohol rather like disulfiram (Antabuse) and can cause severe nausea and vomiting.
Griseofulvin can cause an increase in a liver enzyme reducing the concentration of:
- Warfarin (thinning the blood less than required)
- Oral contraceptive (increasing the chance of pregnancy)