Oral terbinafine (Lamisil) in the treatment of fungal infections of the skin and nails.

The efficacy and safety of antifungal drugs depend upon their mode of action, the minimal inhibitory concentration (MIC) and its relationship to the minimal fungicidal concentration (MFC), the spectrum of activity and drug kinetics at the involved site. Terbinafine acts at the fungal cell wall. Its MIC against dermatophytes is the lowest of all currently available systemic antifungal agents. It is the only one with an MIC:MFC ratio of 1:1 so that terbinafine should be effective over very short treatment durations in dermatophyte infections of the scalp, palms and soles, and nail, providing that drug penetration is adequate, as it appears to be. Therapeutic levels persist for a considerable period after the cessation of treatment, also favouring short-duration therapy. Terbinafine is effective against all varieties of dermatophyte. Terbinafine given over 4 weeks or less is effective against Trichophyton of the scalp in children and adults. Its efficacy in zoophilic ectrothrix infection is anecdotal, but it is likely on theoretical grounds. Terbinafine is also effective against pityriasis versicolor and vaginal candidosis, but only topically. As of March 1996, around 3,000,000 patients have been treated worldwide with terbinafine, mostly for 12 weeks for toe-nail onychomycosis. Gastro-intestinal disturbance and minor skin rashes are seen in 5 and 2% of patients, respectively.