FDA Approves New Topical Drug for Head Lice

Megan Brooks

January 19, 2011

January 19, 2011 (UPDATED January 27, 2011) — The US Food and Drug Administration (FDA) has approved spinosad (Natroba Topical Suspension 0.9%, ParaPRO) for the treatment of head lice infestation in people aged 4 years and older.

Head lice (Pediculus capitis) are spread most often by close person-to-person contact. They are very common among schoolchildren in the United States — second only to the common cold among communicable diseases affecting schoolchildren, according to the Mayo Clinic.

A variety of topical over-the-counter medications and prescription medications are currently available to treat head lice.

"Natroba provides another option for the topical treatment of head lice infestations, which are especially prevalent in the pediatric population," said Julie Beitz, MD, director of the Office of Drug Evaluation III in the FDA's Center for Drug Evaluation and Research, in an FDA statement.

Unlike other medications for head lice, spinosad does not require combing through the hair, according to the manufacturer. A fine-tooth comb may be used to remove dead lice and nits from the hair and scalp, but is not required, according to the company's Web site. The pediculicide spinosad should be used as part of an overall lice management program, with other adjunctive measures including hot-water washing or dry-cleaning of all recently worn clothing, hats, used bedding, and towels; and hot-water washing of personal care items such as combs, brushes, and hair clips.

Spinosad is for topical use only and is not recommended for oral, ophthalmic, or intravaginal use. After shaking the bottle well, the patient or caregiver should apply the product to dry scalp and hair, using the minimal amount needed to cover both. After waiting 10 minutes, the patient or caregiver should thoroughly rinse the head and hair with warm water, being careful to avoid contact with the eyes. If live lice are seen 7 days after the first treatment, topical application of spinosad should be repeated.

Clinical Studies

The FDA's approval was based on the safety and effectiveness of spinosad established in 2 multicenter, randomized, active-controlled studies. The active control was permethrin 1%.

A total of 552 patients received a 10-minute treatment with spinosad. If live lice were seen a week later, a second treatment was applied. The proportion of participants who were lice-free 14 days after the final treatment of spinosad was approximately 86% compared with 44% of the active control group.

In testing, the most common adverse events were application site redness (3%), redness and irritation to the eyes (2%), or application site irritation (1%). These events compared favorably with those seen with permethrin 1%, which was associated with erythema at the application site in 7%, ocular erythema in 3%, and irritation at the application site in 2% of participants.

Use in Special Populations

The safety of spinosad in children younger than 4 years old has not been established, the FDA notes.

The agency adds that it is particularly important not to use the product in infants because it contains benzyl alcohol, which has been associated with serious adverse reactions, including death, when applied topically to the skin of children younger than 6 months.

Although clinical studies did not enroll sufficient numbers of participants 65 years and older to examine whether they respond differently than younger participants, other reported clinical experience has not detected differences in responses between elderly and younger patients.

Spinosad is a pregnancy category B medication, with no adequate and well-controlled studies of spinosad topical suspension in pregnant women. Furthermore, human studies did not determine the absorption of benzyl alcohol contained in spinosad topical suspension. Although reproduction studies in rats and rabbits demonstrated no teratogenic effects, animal reproduction studies do not always predict human response, and this drug should be used during pregnancy only if clearly needed.

Regarding nursing mothers, spinosad is not systemically absorbed and therefore is not present in human milk, but benzyl alcohol contained in the topical suspension may be systemically absorbed through the skin. Because the amount of benzyl alcohol excreted in human milk with use of spinosad topical suspension is unknown, caution should be used when a lactating woman is treated. To avoid infant ingestion of benzyl alcohol, a lactating woman may wish to pump and discard breast milk for 8 hours after use of spinosad topical suspension, which represents 5 half-lives of benzyl alcohol.

More information on this drug approval is available on the FDA Web site.

Laurie Barclay, MD, contributed to this news article.

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