The successful treatment of Trichophyton rubrum nail bed (Distal subungual) onychomycosis with intermittent pulse-dosed terbinafine

Background: The standard treatment of Trichophyton rubrum nail bed onychomycosis (or distal subungual onychomycosis [DSO]) with daily terbinafine for 12 weeks involves treating for a fixed period shorter than the time required for complete replacement of the nail bed and overlying nail plate by normal growth. The same total amount of terbinafine pulse-dosed for approximately 12 months would treat the patient until normal replacement of the mycotic nail bed has occurred. Objectives: To determine the effectiveness of intermittent administration of oral terbinafine (250 mg/d for 7 consecutive days every 2-4 months) to cure DSO and to determine the maximum effective treatment interval. Design: A prospective, nonrandomized, open study of sequential groups of office patients. Setting: A private dermatology practice. Methods: A sequence of 4 groups of office patients with DSO (n=10-20 each) were treated with pulse-dosed terbinafine for 7 consecutive days at intervals of 2, 3, and 4 months, respectively. In each group, treatment was continued until the distally advancing new nail bed and nail had completely removed the mycotic defect or failure of fungistasis was detected. Main Outcome Measurement: Results were determined by monthly evaluation. Cure was noted as complete replacement of the mycotic nail bed and overlying nail plate (ascertained by monthly metric measurements of the mycosis-free nail bed and overlying nail place distal to the proximal nail fold). Treatment failure was noted when the mycosis-free proximal portion of the nail bed failed to increase in correspondence with the distally directed movement of the nail bed and overlying nail. Results: Thirty-nine (93%) of the 42 patients in the first 3 groups were cured (95% binomial confidence interval, 67%-100%) with no evidence of decrease in efficacy. However, the group of patients who received the 7-day pulse treatment every 4 months experienced significantly more failures (P<.01), and cures dropped to 10 of 17 cases. Conclusion: Terbinafine is an effective treatment for DSO when pulse-dosed for 7 days every 3 months but not every 4 months.