Head-lice infestation is prevalent worldwide, especially in children 3 to 11 years old.

Topical insecticides (i.e., pyrethroids and malathion) used as a lotion, applied twice at an interval of 7 to 11 days, are typically used for treatment. Resistance of lice to insecticides, particularly pyrethroids, results in treatment failure.

For difficult-to-treat head-lice infestation, oral ivermectin, given twice at a 7-day interval, had superior efficacy as compared with topical 0.5% malathion lotion, a finding that suggests that it could be an alternative treatment.

References:
Oral Ivermectin versus Malathion Lotion for Difficult-to-Treat Head Lice. NEJM, 2010.