Oral ivermectin is effective against hard-to-treat head lice

A clinical trial in patients with head lice that failed to be eradicated by topical insecticide compared the efficacy of oral ivermectin with that of malathion lotion. A total of 812 lice-infected patients, representing 376 households, were enrolled. All had unsuccessfully used topical insecticide 2 to 6 weeks before enrollment. Members of each household received either ivermectin pills (400 mcg per kilogram of body weight) or 0.5% malathion lotion, each administered on days 1 and 8. More than three-quarters of the study population was female (median age, 10 years). About 15% of households had more than 3 family members with an infestation. Almost 11% of enrollees either were lost to follow-up or did not complete the study.

On day 15, 95.2% of the ivermectin group were free of head lice compared with 85% of the malathion group. At the household level, 92.4% in the ivermectin group were free of head lice compared with 79.1% of households in the malathion group. On day 15, 8 patients in the ivermectin group and 31 in the malathion group still had live lice and entered an extension phase of the study, during which these patients were switched to the alternative treatment. Among these patients, almost all no longer had head lice at day 29. Two serious adverse events were reported: a seizure in a 7-year-old girl in the ivermectin group and a severe headache in an 11-year-old girl in the malathion group (Chosidow O, et al. Oral ivermectin versus malathion lotion for difficult-to-treat head lice. N Engl J Med. 2010;362[10]:896-905).

Commentary
Ivermectin is a commonly used antiparasitic agent. It may now offer a reasonable alternative treatment for difficult-to-treat head lice. I would, however, suggest saving this choice for patients similar to those described in this study-persons in whom conventional therapy has failed to eradicate lice.-MB