Doubled dose of oral terbinafine is required for Microsporum canis tinea capitis.

Fourteen children, ages 1-15 years, with Microsporum canis tinea capitis were given oral terbinafine for 4 weeks at the recommended daily dose according to their weight: 10-20 kg, 62.5 mg; 20-40 kg, 125 mg; > 40 kg, 250 mg. Because none of the patients had clinically responded to treatment by week 4 the dose of terbinafine was doubled (up to 250 mg) for an additional 4-8 weeks in six patients, and continued at the original dose in six patients. Two patients dropped out of the study. On final evaluation, four patients were cured after 8-12 weeks of treatment. All cured patients received the doubled dose of terbinafine, except for one who was on the usual adult dose of 250 mg from the onset. Oral terbinafine was well tolerated by all but one patient, who experienced gastrointestinal disturbance and slightly raised transaminase levels during the first 4 weeks of treatment. Terbinafine side effects were not correlated with dosage or duration of treatment. We conclude that oral terbinafine should be dosed for M. canis tinea capitis at a revised schedule according to body weight: 10-25 kg, 125 mg/day and > 25 kg, 250 mg/day. The appropriate duration of terbinafine treatment remains to be determined.