Pharmacotherapeutic group: Antifungal for topical use. ATC Code: D01AE15.
Pharmacology: Pharmacodynamics: Mechanism of Action: Terbinafine interferes specifically with fungal sterol biosynthesis at an early step. This leads to a deficiency in ergosterol and to an intracellular accumulation of squalene, resulting in fungal cell death. Terbinafine acts by inhibition of squalene epoxidase in the fungal cell membrane. The enzyme squalene epoxidase is not linked to the cytochrome P-450 system. Terbinafine does not influence the metabolism of hormones or other drugs.
Terbinafine is an allylamine which has a broad spectrum of antifungal activity in the fungal infections of the skin caused by dermatophytes such as Trichophyton (e.g. T. rubrum, T. mentagrophytes, T. verrucosum, T. violaceum), Microsporum canis and Epidermophyton floccosum. At low concentrations terbinafine is fungicidal against dermatophytes, moulds and certain dimorphic fungi. The activity against yeast is fungicidal (e.g. Malassezia furfur) or fungistatic, depending on the species.
Pharmacokinetics: Absorption: Less than 5% of the dose is absorbed after topical application to humans; systemic bioavailability is therefore very low.
Distribution: Following application for 7 days, concentration of terbinafine in excess of those required for fungicidal activity are available in the affected stratum corneum for at least 7 days after treatment cessation.