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Terbinafine hydrochloride (Lamisil AT) gel, an allylamine (a class that is fungicidal, unlike the azoles, which are fungistatic), is an over-the-counter third-generation antifungal that has recently achieved widespread commercial distribution in the United States.1–7 Terbinafine is also available as a cream, a solution, and a spray. In patients aged 12 years or older, it is indicated for once-daily treatment of tinea pedis. While most antifungal agents are indicated for 14 days of treatment, terbinafine gel requires only 7 days' application because it is highly lipophilic and keratophilic and maintains high therapeutic levels in the skin. It is currently indicated only for interdigital use.

A study of terbinafine 1% emulsion gel in 101 patients with tinea pedis treated once daily for 1 week showed that at 8 weeks the gel was effective in 59% of patients vs 29% of patients receiving placebo; 81% of patients treated with terbinafine gel had negative microscopic findings and culture, while only 33% of patients receiving placebo had negative findings.2

A double-blind, placebo-controlled, randomized, parallel-group study evaluated the topical 1% emulsion gel formulation of terbinafine for efficacy and safety in the treatment of tinea corporis/cruris in 83 patients.3 The investigators measured mycologic cure and effectiveness of treatment (mycologic cure plus no or minimal signs and symptoms) on day 7; at weeks 2, 4, and 8; and at the end of the study. At the study's end, rates of mycologic cure were 83% for terbinafine 1% emulsion gel and 27% for placebo gel, with respective rates for effective treatment of 83% and 21%. Complete cure was recorded for 59% of patients receiving terbinafine 1% emulsion gel and 13% of patients receiving placebo gel.3

In an open, prospective, comparative, randomized, parallel-group study involving 65 patients, researchers evaluated the efficacy and safety of topical 1% emulsion gel of terbinafine once daily for 1 week (33 patients) vs 2% ketoconazole cream once daily for 2 weeks (32 patients) to treat tinea corporis and tinea cruris.6 Mycologic cure was 94% for terbinafine emulsion gel and 69% for ketoconazole cream; 1 patient in the terbinafine group and 3 in the ketoconazole group suffered contact dermatitis. While not specifically indicated, terbinafine appears effective against tinea versicolor. In a prospective, double-blind, placebo-controlled, randomized, parallel-group, comparative, multicenter study of 61 patients (31 receiving terbinafine gel and 30 a placebo gel once daily for 7 days with 8 weeks of follow-up), 28 patients in the active group and 29 in the placebo group were evaluable for efficacy.1 Using an intent-to-treat efficacy analysis, the researchers found 21/28 (75%) patients were cured in the terbinafine gel-treated group, compared with 4/29 (14%) in the placebo group with outside effect.

A double-blind, placebo-controlled study was conducted to evaluate the efficacy of 1% and 3% terbinafine gel for 5 days in 84 outpatients with tinea pedis.7 The primary efficacy end point was the percentage of patients with effective treatment (negative microscopic findings and culture with only mild erythema/desquamation/pruritus [total score, ≤2]) at study end point (last post-baseline observation up to and including week 6). The efficacy rates/mycologic cure rates with terbinafine 1% and 3% emulsion gel were significantly higher than with placebo (86%/97% and 68%/89%, respectively, vs 11%/22%). The study authors concluded that terbinafine 1% emulsion gel used once daily for 5 days is an effective, short-duration treatment of tinea pedis.

In conclusion, the over-the-counter terbinafine gel is a very attractive, effective antifungal treatment. While indicated only for interdigital tinea pedis, it is undoubtedly effective against other cutaneous fungal infections. Its effectiveness compared with newer antifungal gels and foams is not known.

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