Eradicating Otomycosis with Terbinafine Solution: Basic and Clinical Investigation

Background: Otomycosis still remains intractable in clinical practice, likely because topical antifungal agents lack efficacy or are potentially toxic to the inner ear end organs. Objectives: The aim of this study was to investigate whether terbinafine solution is a potential candidate for treating intractable otomycosis in humans. In addition, the toxic effect on the inner ear was also assessed by animal models treated with terbinafine. Methods: Guinea pigs were instilled with 0.1 mL terbinafine (10 and 25 mg/mL) in the left round window membrane. At 2 weeks after treatment, all animals underwent an inner ear test battery and were then sacrificed for morphological study. Clinically, 20 patients with otomycosis were treated with terbinafine solution at a dosage of 0.4 mg. Results: All terbinafine-treated animals showed intact inner ear function when total dosage of terbinafine was <2.5 mg, which was further confirmed by morphological study. Subsidence of otomycosis was achieved in all 20 patients 1 week after treatment with terbinafine (0.4 mg) without untoward effect. No evidence of recurrence was noted 1 year after treatment. Conclusion: The paucity of inner ear toxicity of terbinafine even at a dosage of 2.5 mg was identified in guinea pig models morphologically and physiologically. Topical application of terbinafine solution at a dosage of 0.4 mg may be a potential treatment for otomycosis in humans.