Head lice affect millions of school-aged children each year, and as the FDA noted in a Consumer Health Information release last year (“Treating Head Lice,” January 2014), this is a year-round problem that peaks in September and January, when children return to school.
Treatment can be complicated, time-consuming, and not always effective. In March 2014, Kyong Sup Yoon and colleagues reported in Journal of Medical Entomology (2014;51:450-57) that head-lice resistance to the widely used pyrethrin-based products, specifically permethrin (the synthetic version of pyrethrin), had grown to 99.6% in a recent period studied. If live lice are combed out of hair after over-the-counter (OTC) treatment, the person is likely dealing with a resistant strain of head lice that may require a product from the new generation of FDA-approved therapies.
Head-lice therapies that came to market more than 25 years ago are considered first-generation treatments. These include the FDA-approved OTC medications containing the active ingredients permethrin and pyrethrin.
The other medications in this group are still prescription-only because they contain black-box warnings of potential severe side effects, as seen with products containing lindane, an organochlorine insecticide; or because they are associated with significant side effects that have led to label changes in recent years, as seen with the organophosphate insecticide malathion.
In November 2012, the American Academy of Pediatrics (AAP) released a policy statement, “Pesticide Exposure in Children” (Pediatrics. 130:e1757-e1763). The statement included 3 classes of pesticide that serve as active ingredients in several widely used head-lice preparations: organochlorides, listing lindane; organophosphates, listing malathion; and even what are considered very safe pyrethrins, listing permethrin. These 3 active ingredients can be purchased as head-lice treatments either OTC or by prescription.
The AAP recommends that health-care professionals and government agencies limit exposure to each of these products and notes that some health-care providers do not recognize cases of acute pesticide poisoning. Therefore, many of these poisonings can go unreported. Strengthening the identification and reporting of such events is a goal of the AAP policy, but avoiding these situations altogether is the underlying mission.
In 2012, the AAP included the following guidance in its Red Book (redbook.solutions.aap.org): “For treatment failures not attributable to improper use of an over-the-counter pediculicide, malathion, benzyl alcohol lotion, or spinosad suspension should be used.”
The AAP has removed lindane from the Red Book recommended-treatment list and has added a second-generation head-lice medication (the aforementioned benzyl alcohol lotion) as well as a third-generation product (the aforementioned spinosad suspension) to be used in cases of treatment-resistant lice. These agents are classified by the FDA as pregnancy category B.
Another third-generation offering, ivermectin, has a pregnancy category C classification. Unlike spinosad, ivermectin has been shown to be systemically absorbed. Retreatment is usually not necessary and nit-combing is not required with either spinosad or ivermectin. According to information from the CDC, only spinosad kills live lice as well as unhatched eggs (cdc.gov/parasites/lice/head/treatment.html).
Several new agents can help resolve cases of head lice that are resistant to older drugs.
Mimi Burnside, BSN, RN, formerly a nurse at Cardinal Glennon Children’s Medical Center (St. Louis, Mo.), is now an elementary-school nurse in Westfield, Ind., with 6 children of her own.