Terbinafine (Lamisil) is a second-generation allylamine that is related to naftifine; however, it is 10 to 100 times more potent in vitro. It is fungicidal, whereas griseofulvin, ketoconazole, itraconazole, and other azole derivatives are all fungistatic. Because it is fungicidal, duration of therapy is shorter, and relapse rates are less than with other oral or topical therapies. Terbinafine acts by inhibiting squalene epoxidase and thereby decreasing synthesis of ergosterol, an essential component of fungal cell membranes. It is highly lipophilic and concentrates in the stratum corneum, sebum, and hair follicles. Slightly better cure rates are attained with b.i.d. than with daily dosing.
