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Pill Found to Outdo Lotion in Tough Head-Lice Cases

Head lice are itchy, nasty nuisances that can be hard to get rid of. Can a pill provide relief? A new study has found that in tough cases, an oral medication kills the parasites more effectively than a prescription lotion applied to the scalp.

The study, published Thursday in the New England Journal of Medicine, compared ivermectin -- an antiparasitic drug used for human river-blindness cases and animal parasites -- with a lotion containing the insecticide malathion.

Ivermectin is not approved for use in the U.S. for head lice. Malathion, a topical insecticide available by prescription, is usually used as a head-lice treatment after over-the-counter topical products have failed.

Researchers studied 812 people in 376 households in seven areas in the world. All participants had head lice even after treatments with over-the-counter lotions or malathion-containing prescription lotions.

The households were randomly assigned to get two doses of an ivermectin pill plus an inactive lotion, or malathion lotion plus a placebo pill. In the ivermectin group, 95% of the participants were lice-free after two weeks, compared with 85% of the malathion group. Of households, 171 of 185 using ivermectin were head-lice-free, compared with 151 of 191 using malathion.

Ivermectin ends up in the blood that head lice feed on, and it blocks the ability of louse nerves to communicate, killing the creatures.

The 10 percent difference in effectiveness between ivermectin and malathion lotion is significant, said lead author Dr. Olivier Chosidow, head of dermatology at Henri Mondor Hospital in Creteil, France. “If you still have one or two lice you’ll be reinfested one or two weeks later,” he said.

But he added that ivermectin should not be used as a first-line treatment, even though head lice are developing resistance to over-the-counter products and malathion. Lice can become resistant to ivermectin too.

The medication, like malathion, can cause problems for some people, he added. In the study, seven people of 398 taking ivermectin developed impetigo (a skin infection), nausea, vomiting, gastroenteritis or convulsions. One child had a seizure later found to be unrelated to the medication. Six of the 414 people in the malathion group had rashes or hives, gastroenteritis or headache.

“This gives us another tool in the arsenal,” said Timothy Gibb, an extension entomologist with Purdue University in West Lafayette, Ind. “It makes it much more difficult for the head lice to develop a resistance to all of these [chemicals] at once.”

Not everyone is convinced that a new drug treatment is warranted, especially one that comes with side effects, even if rare.

“In the grand scheme of what kids get, head lice is minimal,” said Dr. Barbara Frankowski, professor of pediatrics at the University of Vermont College of Medicine. “You never want the cure to be worse than the problem you’re trying to get rid of.”

The study was funded by Johnson & Johnson-Merck Sharp & Dohme Consumer Pharmaceuticals, a joint venture between Johnson & Johnson Consumer and Merck Sharp & Dohme. Merck manufactures ivermectin. Some authors were employed by or had financial relationships with the companies.

jeannine.stein@latimes.com


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