Terbinafine

Terbinafine hydrochloride (Lamisil in UK, US, France, Canada, Romania and Hungary, also sold under the name Terbisil) is a synthetic allylamine antifungal. It is highly lipophilic in nature and tends to accumulate in skin, nails, and fatty tissues. As a generic it is sold under the name Zabel in Australia. It is now also available as a generic in the U.S.

Pharmacology
Terbinafine hydrochloride is a white fine crystalline powder that is freely soluble in methanol and methylene chloride, soluble in ethanol, and slightly soluble in water.

Like other allylamines, terbinafine inhibits ergosterol synthesis by inhibiting squalene epoxidase, an enzyme that is part of the fungal cell wall synthesis pathway.

Indications
Terbinafine is mainly effective on the dermatophytes group of fungi.

As a 1% cream or powder it is used for superficial skin infections such as jock itch (Tinea cruris), athlete's foot (Tinea pedis) and other types of ringworm.

Oral 250mg tablets are often prescribed for the treatment of onychomycosis of the toenail or fingernail due to the dermatophyte Tinea unguium. Fungal nail infections are located deep under the nail in the cuticle to which topically applied treatments are unable to penetrate in sufficient amounts. The tablets may, rarely, cause hepatotoxicity, so patients are warned of this and may be monitored with liver function tests. Alcohol consumption should also be avoided while taking terbinafine.

Specific US issues
Many health insurance companies consider these infections to be a cosmetic problem, and either do not cover the cost of the months-long course of Lamisil, which can run into the thousands of dollars, or recommend use of less expensive alternatives like fluconazole.

FDA approval

The FDA has approved the first generic versions of prescription Lamisil (terbinafine hydrochloride) tablets. The remaining patent or exclusivity for Lamisil expired on June 30, 2007.

On September 28, 2007, the U.S. Food and Drug Administration stated that Lamisil (terbinafine hydrochloride, by Novartis AG) is a new treatment approved for use by children aged 4 up. The antifungal granules that can be sprinkled on a child's food to treat ringworm of the scalp, Tinea capitis.