Terbinafine is an orally and topically active allylamine antifungal agent with fungistatic and fungicidal action. Its mechanism of action is the competitive inhibition of squalene epoxidase which leads to squalene accumulation and ergosterol depletion in the cell membrane. Clinically relevant pathogens can include but are not limited to: Aspergillus spp., Candida spp., Blastomyces dermatitidis, Histoplasma capsulatum, Emydomyces testavorans, Ophidiomyces ophiodiicola, and Batrachochytrium dendrobatidis. Terbinafine is an antifungal drug that has been used successfully in humans with few adverse effects. It is not licensed in the United States for systemic use in veterinary medicine but is routinely used in an extra label manner to treat fungal infections. Terbinafine has been well tolerated in domesticated and non-domesticated animals that have been studied. The studies that are available suggest that species differences exist in pharmacokinetics and further research is necessary to establish recommended doses in individual species. Due to the variation, terbinafine should be investigated on a species-by-species basis to determine its effective and safe use, thus ensuring the wellbeing of animals.
Harvill et al. (2026) studied this question.