Promising early returns seen on newer therapies against lice

June 2003

SAN FRANCISCO — Head lice may not be painful or lead to serious infection, but it sure can be a pain to manage and control.

A recent rise in resistance has precipitated a need for new treatment strategies, stronger treatments and new agents to control infestations. New knowledge about the common head louse has driven researchers to find new ways to employ commonly used drugs and some common household items to control lice. The demand for new products has driven pharmaceutical companies to come up with new therapies.

So far the news has been positive. Early studies on several novel therapies have returned effective kill rates. So, while it can be assured that lice will continue to receive a lot of attention, pediatricians can stay confident they can help effectively control outbreaks.

Separating fact from fiction

Head lice receive so much attention that sometimes it is hard to separate fact from fiction. There are an increasing number of reports that head lice are more common in white and Asian children than black children.

“North American head lice do not typically affect the hair of American blacks,” said Lawrence Schachner, MD, professor of pediatrics and dermatology at the University of Miami School of Medicine. In Africa, where head lice are a dominant problem, a different species of louse predominates, he said.

One unfortunate myth that has circulated about lice is that infestation is a problem of poor children. While lice infestation is a prominent problem in poor environments, lice also affect middle and upper class children, and it is especially a problem for children of pediatric dermatologists, said Schachner.

Many case studies have reported a higher prevalence of lice among girls. Though girls may share brushes and hats more often than boys, the gender difference is not as great as it is perceived, according to Schachner.

One study found that louse infestation among children who shared a locker at school or who had an unassigned clothing hall hook on which to hang their jacket had more frequent head lice than children who had their own locker or had an assigned hook.

“Unlike scabies, lice is a clothing to clothing, or a fomite off the body infestation,” said Schachner.

In a recent policy statement, the AAP addressed another common myth, namely “no nit policies.” Under no nit policies, children were excluded from school until all traces of nits were cleared from the scalp.

However, it seems that no nit policies only led to economic hardships for parents, causing missed time from work and school, and did more harm than good. In a recent policy statement, the AAP said that children should be permitted to return to school the day after treatment.

Growing resistance problem

One sure thing about head lice is that resistance is a growing problem. But knowing a little about the bug itself may open up new treatment options, according to Schachner.

Traditionally, lindane, malathions and natural permethrins, such as RID A200, have been used to treat lice. Newer agents such as 1% permethrin (Nix, Pfizer), anise and Hair Clear (Quantam), an herbal product, have proven effective.

While older medicines still may be effective in treating most lice, there is a growing problem with resistance. Several strategies have been proposed to combat the problem, falling into three essential categories: novel treatment modalities, stronger therapies and novel agents.

The North American louse has plates aligning its thorax with breathing apparatus in between. If the apparatus is coated with a thick viscous substance, like petroleum jelly (Vasoline), the bug can not breathe, said Schachner.

The louse also has a well-developed gut containing symbiotic bacteria. Since lice require human blood for food, getting a sufficient blood level of trimethoprim-sulfamethoxazole (TMP-SMX) in the patient will eliminate those bacteria, and therefore the bug. TMP-SMX should be used to treat lice in similar doses as otitis media, said Schachner.

Stronger permethrin at 5% dilution has been used to treat scabies for years and may also be useful in treating resistant head lice as well.

Perhaps the best promise for resistant head lice are novel agents and reintroduced agents. Malathion (Ovide lotion, Medicis) is a rapid pediculicide and effective ovicide, and one treatment is usually effective. However, the product contains only 5% active ingredient and 78% isopropyl alcohol — which is highly flammable — and current guidelines suggest leaving it in for eight to 12 hours.

Some smaller studies have suggested that shorter therapy, down to 15 minutes to two hours, may be equally as effective as the eight to 12 hour treatment, but the evidence is at this point preliminary, according to Schachner.

The most recent addition to the lice treatment market is Hair Clean 1-2-3, an herbal product containing oil of anise and Ylang Ylang oil. There has only been one study on Hair Clean, but it did produce a 90% cure rate.

For more information:

• Schachner L. Scabies & lice: tricks & treatment. Presented at the American Academy of Dermatology 61st Annual Meeting. March 21-26, 2003. San Francisco.

• Dr. Schachner has no direct conflict with any products mentioned in this article.