Econazole

Econazole is a topical imidazole antifungal used for dermatophytosis, cutaneous candidiasis, pityriasis versicolor and vulvovaginal candidiasis. Systemic absorption is negligible. Local irritation is the main adverse effect.

Class. Imidazole antifungal.

Mechanism. Inhibits CYP51 and ergosterol synthesis, with direct membrane effects at higher concentrations.

Pharmacokinetics. Less than 1% absorbed through intact skin; vaginal absorption is low and rises slightly with the pessary. Hepatic metabolism of the small absorbed fraction.

Skin infection (tinea pedis, corporis, cruris, cutaneous candidiasis). Cream 1% applied once or twice daily; duration 2 to 4 weeks, with tinea pedis often 4 weeks.

Pityriasis versicolor. Cream 1% once or twice daily for 2 to 3 weeks.

Vulvovaginal candidiasis. Pessary 150 mg nightly for 3 nights.

Loading dose, maintenance dose and titration. Not applicable. Maximum: apply no more than twice daily.

Children. Topical cream is used from infancy under specialist advice; avoid occlusive dressings.

Main alternatives. Clotrimazole or miconazole; terbinafine for nail or extensive tinea.

Contraindications. Hypersensitivity to imidazoles.

Serious adverse effects. Allergic contact dermatitis and, rarely, severe local reaction.

Common adverse effects. Burning, itching, erythema and local irritation.

Interactions. Negligible with topical use; isolated reports of raised INR with warfarin. Weakens latex.

Common prescribing errors. Stopping early, applying to broken skin or the eye, and using occlusion.

Special groups. - Pregnancy: avoid in the first trimester unless essential; acceptable thereafter. - Breastfeeding: limited data; do not apply to the nipple before feeding. - Children: acceptable on small areas. - Older adults: usual doses. - Kidney impairment: no adjustment. - Liver impairment: no adjustment.

Formulations. Cream 1%; vaginal pessary 150 mg.

Administration. Wash and dry the area; apply a thin layer to the rash and a margin beyond it; insert pessaries high in the vagina at night.

Baseline. Confirm the diagnosis, ideally with microscopy of skin scrapings.

Monitoring. Clinical response at 2 weeks; INR if the patient is on warfarin.

Stopping thresholds. Stop for contact dermatitis or marked irritation.

Referral and escalation. Review for treatment failure, nail or scalp involvement, or extensive disease.