Can topical ivermectin become a first-line treatment for head lice?

Acta Eruditorum

Abby Van Voorhees

Dr. Van Voorhees is the physician editor of Dermatology World. She interviews the author of a recent study each month.

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In this month’s Acta Eruditorum column, Physician Editor Abby S. Van Voorhees, MD, talks with David M. Pariser, MD, about his recent New England Journal of Medicine article, “Topical 0.5 percent Ivermectin Lotion for Treatment of Head Lice.”

Dr. Van Voorhees: Let’s start by reviewing the problems with current therapies for head lice. Do these have problems with intolerance or resistance?

Dr. Pariser: Yes to both. Current head lice therapies, which include permethrin and malithion-based products, do have issues with acceptability, scalp irritation, and, most importantly, a significant incidence of resistance. That’s 50 percent or more in some studies. It’s a real problem.

Of course head lice are as much a social problem as a medical one. A kid has lice, they’re out of school, the parents are out of work. A lot of school nurses are very paranoid about it; some schools have a no-nit policy, and if the kids are found with one nit they are kicked out of school and the parent has to come home and get them it’s a huge issue. And there are a lot of psychosocial effects to head lice infestations people have connotations of poor hygiene and uncleanliness, which it has nothing to do with, but people have that in their heads. [pagebreak]

So there has been a therapeutic need for something new. There isn’t any resistance to ivermectin at this time there may be down the road, but for now it’s a new option, the lice haven’t seen it, and the other products that are available are not labeled for young children, while this one is. 

Dr. Van Voorhees: What is known about ivermectin? How has it been used previously and for what indications?

Dr. Pariser: It has been used for systemic treatment of parasitic diseases, onchocerciasis, and strongyloides most commonly. That’s been its major use around the world; in developing countries where those problems are significant the use of ivermectin has really helped with those diseases. I just came back from the Regional Dermatology Training Centre in Tanzania where the Academy had a CME course on tropical medicine so I got to see some of its uses there.

Ivermectin is also used off-label for treatment of scabies and is very effective with one or two doses. There were no topical forms of ivermectin prior to this study; whether the topical form of it will be studied for other indications, such as scabies, remains to be seen. [pagebreak]

Dr. Van Voorhees: Tell us about your study of head lice.

Dr. Pariser: This was a multi-center study. It was industry-sponsored; the investigators helped develop the protocol. There were 16 sites with two separate, identical studies that were IRB-approved.

In all we had 781 subjects in a double-blind, placebo-controlled study. They were all included in the intention-to-treat population and 780 were included in the safety data we had one person who signed a consent form but never got the drug. We based our results on an index case, defined as the youngest person in the household, but everyone in the household was treated with the idea of minimizing re-infestation. The treatment was a one-time, 10-minute application. That was it, put it on dry hair for 10 minutes and then rinse it off. No combing, no nothing.

Dr. Van Voorhees: Was it effective? How do these results compare with current first- and second-line treatments?

Dr. Pariser: We had a pretty good success rate. On day two, 94.9 percent of patients treated with the active compound were louse- and nit-free, as were 31.3 percent with placebo. By day eight, 85.2 percent of the active treated group and 20.8 percent of the placebo group were louse- and nit-free. On day 15, 73.8 percent of the active group and 17.6 percent in the placebo group were louse- and nit-free. The 15-day louse and nit-free rate of 73.8 percent probably represents re-infestation since 94.9 percent were louse- and nit-free on day two. There are other possible causes perhaps some unhatched eggs that didn’t get killed and hatched later or treatment failures. [pagebreak]

The current treatments, permethrin and malithion-based products, have about a 50 percent effectiveness rate. They require multiple treatments and they require nit combing, which is a tedious process.

Dr. Van Voorhees: Were there any safety concerns?

Dr. Pariser: They were really very minimal. There were a few people who reported itching and irritation after the one-time application, but it’s hard to know how much of that was the result of the underlying infestation. It was very well-tolerated; there were no systemic side effects or cases of allergic or contact dermatitis. And this was in very young subjects. 

Dr. Van Voorhees: Do you see this replacing our current therapies? Is there a down-side to utilizing this approach?

Dr. Pariser: I don’t think it’s going to replace the current therapies, mostly due to the cost of this medication. Frankly, it’s an expensive drug and it’s a prescription, whereas the other treatments are over-the-counter. Without insurance coverage, it costs much more than the currently available treatments. But if you look strictly at the efficacy, safety, and tolerability, particularly for younger children for which it is labeled where the others aren’t, and at the lack of resistance to the drug that the others don’t have if you look at those objectively, it really could be a first-line treatment. It’s a simple, non-toxic treatment that’s been administered systemically, so people know what the systemic effects are, and they aren’t much. Obviously I’m biased since I did the trial, but the treatment works. 

Dr. Pariser is a professor in the department of dermatology at Eastern Virginia Medical School. His article was published in the New England Journal of Medicine, 2012 (Nov. 1); 367:1687-1693. doi: 10.1056/NEJMoa1200107.