Pharmacology · Other antifungals
Griseofulvin !
Oral antifungal for dermatophytes of skin, hair and nails, classic for tinea capitis in children. It binds microtubules and is deposited in new keratin.
Updated 2026-11-01
Also called: microsize griseofulvin, ultramicrosize griseofulvin
Mechanism of action
Griseofulvin binds microtubule proteins needed for mitosis and disrupts the mitotic spindle, so the dermatophyte cannot divide. It is deposited in keratin precursor cells and binds tightly to new keratin, which then resists fungal invasion; the infected tissue is gradually replaced.
- Griseofulvin binds fungal microtubule proteins
- The mitotic spindle fails and the fungus cannot divide
- New keratin carries the drug and resists infection
Pharmacokinetics
- Absorption
- Variable between people because it dissolves poorly; absorption improves with a fatty meal and with micro- or ultramicrosize forms.
- Distribution
- Concentrates in keratin precursor cells of skin, hair and nails.
- Metabolism
- Liver, mainly to 6-desmethylgriseofulvin; it induces liver enzymes.
- Half-life
- Variable, about 9 to 24 hours.
Indications
- Dermatophyte infections of skin, hair and nails not adequately treated topically: tinea capitis, corporis, pedis, cruris, barbae and unguium. Dermatophytosis (tinea) and onychomycosis →
Adverse effects
Common
- Skin rash and urticaria (the most common reactions)
- Nausea, vomiting, epigastric discomfort, diarrhoea
- Headache, fatigue, dizziness, insomnia, confusion
- Photosensitivity; oral thrush
Contraindications
- Porphyria
- Hepatocellular failure
- Pregnancy or possible pregnancy during treatment
- Hypersensitivity to griseofulvin
Key interactions
- Warfarin-type anticoagulants
- Griseofulvin decreases their effect; the anticoagulant may need adjustment during and after treatment.
- Oestrogen-containing oral contraceptives
- Reduced contraceptive effect and menstrual irregularities; a second method is advised.
- Cyclosporine
- Lower cyclosporine levels and effect.
- Barbiturates
- Lower griseofulvin levels.
- Alcohol
- Nausea, vomiting, flushing, tachycardia and severe hypotension have been reported.
What is monitored
- Periodic kidney, liver and blood-count tests with prolonged therapy
- Skin reactions and sun sensitivity
Administration and safety
- Identify the dermatophyte (KOH, culture or nail biopsy) before starting.
- Microsize and ultramicrosize products are not dosed the same: check the exact product.
- Giving it with a fatty meal improves absorption.
Nursing care
- Rule out pregnancy and teach a second contraceptive method during treatment.
- Teach to avoid intense sunlight and alcohol.
- Report rash, blistering, jaundice or joint pain.
- Men should wait at least six months after the course before fathering a child.
Pregnancy and breastfeeding
Contraindicated: it is teratogenic in animals and cases of conjoined twins have been reported after first-trimester use.
Test yourself
Think of the answer, then tap the question to see it.
What is griseofulvin's mechanism of action?
It binds microtubule proteins and disrupts the mitotic spindle of the dermatophyte.
A teenager on griseofulvin uses an oral contraceptive. What advice follows from the label?
Griseofulvin can reduce the pill's effectiveness; a second birth control method is advised, and pregnancy is a contraindication.
Does griseofulvin treat candidiasis?
No. It acts only on dermatophytes; it is not effective against Candida, histoplasmosis or sporotrichosis.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - GRISEOFULVIN MICROSIZE- griseofulvin tablet (DailyMed (U.S. National Library of Medicine), 2025); Griseofulvin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 61 (McGraw Hill, 2023).
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