Terbinafine, a synthetic allylamine antifungal used commonly in human and veterinary medicine, is efficacious against the 3 most common veterinary dermatophytes (Microsporum canis, M gypseum, Trichophyton mentagrophytes), with a reported minimum inhibitory concentration of 0.03 µg/mL. Terbinafine also exhibits low minimal fungicidal concentrations against most dermatophytes, allowing for higher efficacy and lower relapse rates than those observed with itraconazole. Terbinafine absorbs well orally and, like azole antifungals, is lipophilic and concentrated rapidly in the stratum corneum, reaching high concentrations in the sebum, hair, and nails. The elimination half-life from these tissues is prolonged at 4–5 days, and terbinafine levels in nails and hairs have been shown to remain at mean inhibitory concentrations for 90 days in humans and 37 days in cats posttherapy. Thus pulsatile dosing may be useful for treating dermatophytes in these species. Topical ophthalmic preparations of terbinafine have been shown to be 89% effective in treating human fungal keratopathies, but topical formulations of terbinafine in horses and rabbits exhibited varying results. Terbinafine is associated with a low index of toxicity and few adverse effects.

Although use of terbinafine, relatively new to veterinary medicine, is becoming more common in dogs and cats, use in exotics is limited by lack of data. Of note is the discussion of terbinafine against dermatophytosis, one of the most common causes of skin infection of small mammals and pocket pets. Data regarding efficacy to treat other fungal infections are limited, although small studies may support its use and safety. This report can be especially helpful for practitioners who treat wildlife, avian patients, and other exotic pets.—William Oldenhoff, DVM

Therapeutic review: Terbinafine. Keller KA. J EXOTIC PET MED 21:181-185, 2012.

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