An observer-blinded study of 1% permethrin creme rinse with and without adjunctive combing in patients with head lice.

OBJECTIVES: To determine if NIX (Warner Lambert Healthcare, Morris Plains, NJ) 1% Permethrin Creme Rinse Lice Treatment (1% PLT) without combing will effectively treat >/=95% of patients on day 2 or on day 15; to determine whether combing influences efficacy. STUDY DESIGN: A randomized, observer-blinded study enrolled 95 infested adults and children. All patients were treated with 1% PLT on day 1 and, if still infested, on day 8. One third of households were randomized to the combing group and two thirds to the no-combing group. Efficacy was assessed by: (1) visual inspection on days 1, 2, 8, 9, and 15 and, (2) shampooing/straining on days 2, 9, and 15. The target efficacy was 95%. RESULTS: In the no-combing group, the lice-free rate was 83.1% on day 2 (95% CI, 71.0-91.6), 45.8% on day 8 (before second treatment) (95% CI, 32.7-59.2), 77.6% on day 9 (95% CI, 64.7-87.5), and 78.3% on day 15 (95% CI, 65.8-87.9). Adjunctive combing did not improve efficacy on any day. CONCLUSIONS: In this population, 1% PLT was significantly less than 95% effective and suggests resistance to 1% PLT. The failure of nit removal combing by nonprofessional caregivers to improve efficacy demonstrates the unreliability of combing as adjunctive treatment in this setting.