Dermatology/Antifungal

Antifungals (skin)

also: terbinafine · clotrimazole · ketoconazole · griseofulvin · nystatin

Overview

Treatment of dermatophyte (tinea), yeast (candida, pityriasis versicolor) and seborrhoeic skin infection (cross-references the antimicrobial section).

Mechanism

Terbinafine (allylamine) inhibits squalene epoxidase → ergosterol depletion (fungicidal to dermatophytes). Azoles (clotrimazole/ketoconazole/itraconazole) inhibit lanosterol 14α-demethylase (CYP-dependent) → ↓ergosterol. Griseofulvin disrupts fungal microtubules/mitosis and deposits in keratin. Nystatin (polyene) binds ergosterol → membrane pores (Candida only).

Indications

Tinea corporis/pedis/cruris (topical) & capitis/unguium (oral)
Candidiasis (clotrimazole/nystatin)
Pityriasis versicolor & seborrhoeic dermatitis (ketoconazole)

The agents

Terbinafineallylamine

oral for nails/scalp; topical tinea

First-line for onychomycosis; check LFTs.

Imidazoles (clotrimazole/ketoconazole/miconazole)azole

topical

Broad incl. candida; ketoconazole shampoo for seb. dermatitis/versicolor.

Griseofulvinantimitotic

oral

Tinea capitis (esp. children); teratogenic, enzyme inducer.

Nystatinpolyene

topical/oral (gut)

Candida only — NOT dermatophytes.

Adverse effects

Terbinafine: hepatotoxicity, taste disturbance (can be permanent), GIserious

Azoles: hepatotoxicity + CYP450 interactionsserious

Griseofulvin: photosensitivity, enzyme inductioncommon

Reduces OCP/warfarin efficacy.

Cautions & contraindications

Significant hepatic disease (terbinafine, oral azoles)all

Griseofulvin in pregnancy / porphyria / SLEpregnancy

Interactions

Oral azoles inhibit CYP3A4 (statins, warfarin)
Griseofulvin induces CYP (↓OCP, warfarin)

Monitoring & kinetics

LFTs for oral terbinafine/azoles (longer courses)

Topical for localised tinea/candida; oral for nails, scalp and extensive/resistant disease.

Source: NICE CKS — Fungal skin infections · BNF — Antifungals