Eradicating Head Lice With a Pill

William T. Basco, Jr., MD


May 11, 2010

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

Chosidow O, Giraudeau B, Cottrell J, et al
N Engl J Med. 2010;362:896-905


The worldwide resistance of head lice to pyrethrins is increasing and has stimulated greater interest in identifying alternative therapeutic regimens. One preparation that is increasingly being used is topical malathion 0.5%. This randomized trial compared an oral drug, ivermectin, with topical malathion in households with resistant infestations of head lice. Participants were enrolled as households, and all members of the household had to be infected and had to have had a previous attempt to topically treat at least 1 member for head lice in the 2-6 weeks before enrollment.

Study Summary

Households were enrolled at 7 study centers in 4 countries in 2004. At the initial visit, each member of the household was examined via a standard hair-combing technique to determine the presence of live lice. Households were then equally randomly assigned to the 2 regimens, and the primary outcome was measured at 15 days. If treatment failed at 15 days, the household was switched to the alternate regimen. Participants were not allowed to use combing as a therapy, to chemically treat or color their hair, or to cut it short during the trial. Success was defined as no live lice on day 15, determined by investigator examination and combing.

More than 800 participants in 376 households were enrolled. Initially, 398 participants were treated with ivermectin and 414 were treated with malathion. The median age of the participants was 10 years, and more than 80% of participants were female. Both treatments were administered on days 1 and 8 of the trial. Ivermectin was administered at a dose of 400 µg/kg, given as 3-mg tablets. Research staff applied the malathion preparation to the participants during visits, completely moisturizing each participant's hair and scalp. Once dry, the participant was allowed to leave the study center with instructions to leave the malathion preparation in for 10-12 hours before shampooing. All participants took pills and received lotion application at each visit, but only 1 treatment was active and the other was placebo.

Ivermectin performed better on the primary outcome -- 95.2% of participants were free of live lice at day 15 compared with 85% of the malathion participants (absolute difference, 10.2 percentage points; 95% CI, 4.6-15.7). Primary treatment with ivermectin failed in 8 participants, and malathion failed in 31 participants. All but 1 participant was successfully treated with the alternate regimen after failure of the initial therapy. The participants overwhelmingly preferred oral treatment (78.3% vs 13%; 8.7% indicated no preference). Fewer than 2% of participants in both groups had adverse effects. The investigators concluded that, compared with topical malathion, oral ivermectin had superior efficacy in treating resistant head lice infestation.


Over the past 5 years, I have reviewed several studies that evaluated treatment of resistant head lice, a condition that continues to vex clinicians and patients. Most of the alternative preparations involved topical application of an agent that smothered the lice, and all of these generally low-potential toxicity products tended to perform reasonably well. However, these investigators note the difficulties with patient adherence to topical approaches. With treatment on days 1 and 8 and without the long hours spent combing, oral ivermectin appears to be a huge benefit to parents and children alike and may prove to be a useful alternative.



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