Synthetic allylamine derivatives
Terbinafine, the most commonly used synthetic allylamine deriva-tive, is an allylamine antifungal, which inhibits fungal cell growth by inhibiting an enzyme responsible for the manufacture of ergos-terol.
Terbinafine is well absorbed and distributed throughout the body, especially if taken with food. It’s extensively metabolized; more than two-thirds of the drug is excreted in urine.
Rare cases of liver failure have occurred with terbinafine use, even in the patient with no known history of liver disease. Avoid using this drug if liver disease is suspected, and obtain baseline liver enzyme test results before use.
Terbinafine is thought to inhibit squalene epoxidase, which blocks the biosynthesis of ergosterol, an essential component of fungal cell membranes.
This drug is used to treat tinea unguium (fungal infections of the fingernail or toenail).
Terbinafine clearance is decreased when it’s taken with cimeti-dine and increased when it’s taken with rifampin.
Terbinafine increases plasma levels of caffeine and dex-tromethorphan and decreases levels of cyclosporine. (See Adversereactions to terbinafine.)