GENERIC NAME: terbinafine

BRAND NAME: Lamisil

DRUG CLASS AND MECHANISM: Terbinafine is an antifungal agent that is taken by mouth or applied to the skin. Terbinafine acts by interfering with the ability of fungi to make chemicals called sterols that are an important part of the membrane that surrounds fungal cells and holds them together. This weakens the cell membrane. Oral terbinafine is more effective for treating fungal nail infections than griseofulvin (Fulvicin; Gris-Peg) and itraconazole (Sporanox), two other antifungal agents used for treating fungal nail infections. Topical terbinafine was approved by the FDA in 1993. Terbinafine oral tablets were approved in 1996.

PRESCRIPTION: yes

GENERIC AVAILABLE: yes

PREPARATIONS: Tablets containing 250mg. Cream containing 1% terbinafine, 15gm and 30gm size tubes.

STORAGE: The tablets and the cream should be kept at room temperature, 15-30°C (59-86°F).

PRESCRIBED FOR: Tablets: Fungal infections of the toe, or fingernail, caused by the fungus, tinea unguium.

Cream: Fungal infections of the skin including tinea pedis ("athlete's foot"), tinea corporis, and tinea cruris ("jock itch").

DOSING: Tablets: The usual dose is 250 mg once daily for 6 weeks for treatment of the fingernails, and 12 weeks for treatment of toenails. Alternatively, terbinafine may be given as two tablets (500 mg) once daily for 7 days during the first week of each month for 3 months for toenail infections. For children under 20kg (44 pounds), a dose of 62.5 mg/day and for children between 20 and 40kg (44 and 88 pounds) a dose of 125 mg/day have been recommended. Terbinafine may be taken with or without food.

Cream: The cream is rubbed gently into the affected area (s). The cream usually is applied twice daily for 1 to 4 weeks.

DRUG INTERACTIONS: Rifampin reduces terbinafine blood concentrations, potentially reducing the efficacy of terbinafine, and cimetidine (Tagamet) may increase terbinafine blood levels. The latter effect would not be expected to lead to problems.

PREGNANCY: Studies in animals using large dosages of terbinafine have not demonstrated toxic effects on the fetus; however, there have not been conclusive studies in humans. Since fungal infections of the skin and nails usually are not a serious problem, the manufacturer of terbinafine does not recommend therapy during pregnancy.

NURSING MOTHERS: There is no data on the use of terbinafine during breast-feeding. Nursing mothers should avoid using terbinafine on the breast or taking the drug orally.

SIDE EFFECTS: Terbinafine is a very safe medication. The need to discontinue therapy because of side effects is quite rare. The most frequently reported side effects are diarrhea, and abdominal pain. Increases in liver enzymes, hives, itching and altered taste sensation also have been observed.

Reference: FDA Prescribing Information