New Treatment for Head Lice 'Kills 'Em Dead' After One Application

October 18, 2011

By Fran Lowry

BOSTON (Reuters Health) Oct 17 - Just one 10-minute treatment with spinosad, a new pediculide derived from a naturally occurring soil bacterium, eradicates head lice and nits, researchers said here on Saturday at the 2011 American Academy of Pediatrics (AAP) National Conference and Exhibition.

Spinosad (Natroba) was approved for the treatment of head lice infestations by the U.S. Food and Drug Administration (FDA) in January 2011.

"This is going to really change our landscape in terms of treatment options for head lice because it does not require nit combing, which can be a very arduous overwhelming task for parents and caregivers," Dr. Nicole Rogers, a dermatologist from Metairie, Louisiana, specializing in hair and scalp disorders told Reuters Health.

She presented data on 122 patients between the ages of 2 and 60 years (mean age 12 years) who were randomized to receive spinosad topical suspension or placebo (containing alcohol) as treatment for active head lice infections. Most (87%) were female.

Spinosad 0.5% or 0.9%, which is the formulation approved by the FDA, was applied to dry hair and scalp for 10 minutes and then rinsed with warm water. Vehicle without spinosad was used as the placebo control.

After 7 days, patients were evaluated for efficacy. Patients who showed live lice on day 7 were checked again one week later. Hair samples were also taken at 7 and 14 days post-treatment from patients who were lice free but who had potentially viable nits. After a 10-day incubation period, these patients were deemed to be treatment failures if the nits on the collected hairs hatched.

The study found that on day 7, both spinosad 0.5% and 0.9% groups showed superior results compared with the placebo group, with 93% and 92% being lice free compared with 49% of the placebo group (p < 0.0001).

Similar results were seen on day 14, with both spinosad 0.5% and 0.9% showing superior results to placebo, with 83% and 86% being lice free compared with 26% of the placebo group (p < 0.0001).

Re-infestation rates between day 7 and 14 were 6% for the spinosad 0.9% group, 11% for the 0.5% group, and 50% for the placebo group. Importantly, none of the potentially viable nits that were collected from the spinosad-treated patients hatched.

Spinosad was very well tolerated, with no severe adverse events reported. Spinosad 0.9% had the fewest reported adverse events, Dr. Rogers said.

"Even when we collected potentially viable nits from patients who were lice free on day 7 and day 14 follow-up, none of those nits hatched, which supports the fact that there is considerable ovicidal activity," Dr. Rogers said.

"It's already on pharmacy store shelves as a prescription product, so frustrated parents who have already tried all the over-the-counter options can get a prescription from either their pediatrician or their dermatologist or even their internist."

The study was supported by ParaPRO, which manufactures Natroba.

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