Terbinafine

Terbinafine is an antifungal medication in the allylamine class that is used to treat a variety of superficial fungal infections, including those affecting the skin and nails. It is available in both oral and topical formulations.

Mechanism of Action

Terbinafine acts primarily on dermatophytes, which are a type of fungi that infect the skin and nails. These include species such as Epidermophyton floccosum, Trichophyton mentagrophytes, and Trichophyton rubrum. The drug's fungicidal action stems from its selective inhibition of fungal squalene epoxidase, an enzyme involved in sterol biosynthesis in fungi. This inhibition leads to an accumulation of squalene, a precursor in the pathway, to toxic levels in the fungal cells, thereby resulting in cell death.

FDA Approval and Administration

The U.S. Food and Drug Administration (FDA) first approved the topical formulation of terbinafine in 1992, and subsequently the oral form in 1998. Topical terbinafine is available over-the-counter and comes as a 1% cream or spray for the treatment of various dermatophyte skin infections including tinea pedis (athlete's foot), tinea cruris (jock itch), and tinea corporis (ringworm).

Oral terbinafine, available by prescription only, is typically used for onychomycosis, a fungal infection of the fingernails or toenails. It is commonly prescribed as a 250 mg tablet, taken once daily. The usual course of treatment is 6 weeks for fingernail infections and 12 weeks for toenail infections.

Side Effects and Safety

Terbinafine is generally well-tolerated, but it can cause a number of side effects. The most common side effects include gastrointestinal disturbances, headaches, changes in taste, and rashes. Serious side effects are rare, but terbinafine has been linked to rare instances of acute liver injury, which can be severe and sometimes fatal. For this reason, liver function tests are usually performed before and during treatment with oral terbinafine.

References

• [1] "Terbinafine." LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Institute of Diabetes and Digestive and Kidney Diseases, 2017.
• [2] Gupta, A.K., & Foley, K.A. (2015). Antifungal treatment for pityriasis versicolor. Cochrane Database of Systematic Reviews, 2015(1).
• [3] Sahoo, A.K., & Mahajan, R. (2016). Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatology Online Journal, 7(2), 77-86.

• Dailymed label info on Terbinafine
• FDA Terbinafine

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