Terbinafine in the Treatment of Onychomycosis: Review of Efficacy and Safety

The purpose of this literature research project is to investigate the efficacy and safety of terbinafine when used to treat onychomycosis. Onychomycosis is defined as a fungal infection of the nail, mainly caused by the organism Trichophyton rubrum. The estimated prevalence rate is 8% for the general population of North America, with higher rates occurring in special populations such as the immunocompromised as well as patients afflicted with diabetes. Traditional treatment methods have not been as effective and safe as terbinafine therapy. This allylamine agent inhibits the enzyme squalene epoxidase, crucial to the ergosterol biosynthesis pathway. In addition to impeding growth due to a depletion of ergosterol, which is a vital component of the plasma membrane, a toxic, intracellular accumulation of squalene occurs. Because squalene epoxidase is not cytochrome P-450 dependent, significantly less drug interactions occur. Terbinafine is a broad range antifungal, with a minimum inhibitory concentration and minimum fungicidal concentration much lower than traditional treatments. The mycological cure rate across 20 studies is 80.1% ± 2.3% (mean ± std. error), which is superior to griseofulvin, itraconazole, ketoconazole, and fluconazole. The frequency of adverse effects was minimal and not significantly different when compared to placebo. When terbinafine is used in concomitantly with a topical medication, increased cure rates, decreased failures, and less relapses have been reported. Based to its efficacy rates, broad spectrum use, excellent safety profile, and decreased possibility of drug interactions, terbinafine should be the drug of choice for treatment of onychomycosis in adults and special populations