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.
