Oral Ivermectin Versus Malathion Lotion for Difficult-to-Treat Head Lice

Published - Written by Karen Buckley

In a multicenter, controlled trial, Chosidow et al. looked at 812 patients in 376 households with live lice not eradicated by topical insecticides used 2 to 6 weeks before enrollment. All patients received tablets, either ivermectin or a placebo, and malathion lotion or a placebo lotion. Oral ivermectin was found to be superior to topical malathion lotion in eradicating head-lice infestation.

“Here’s a simple, efficacious treatment for a highly prevalent condition,” said Dr. Lindsey Baden, deputy editor at NEJM.

Current standard treatment for lice starts with a topical lotion, often a pyrethyroid-based insecticide, applied twice at an interval of 7 to 11 days. A second application is needed in order to kill lice that may have hatched from eggs surviving the first treatment. Adherence to topical insecticide regimens is poor, and there is an increasing bug resistance to these lotions.

While it’s not frequently used in the United States, oral ivermectin is used regularly in developing countries to treat parasitic infections. No significant safety concerns have been identified to date.

A previous, non-controlled study with 26 patients found that a single, standard dose (200 μg
per kilogram of body weight) of ivermectin only eradicated head lice in 6 patients. This trial used an oral dose of 400 μg per kilogram of ivermectin.

The researchers note, “Restricting the use of ivermectin for headlice infestation to the target population in our study (i.e., patients with infestation in whom a topical insecticide failed) should limit the risk of the emergence of resistance, but long-term surveillance will be mandatory.”

What do you recommend for a patient with persistent head lice? Given the data in this study, would you favor the use of oral ivermectin in your practice?