Head lice infestation (pediculosis) is a common and stigmatizing problem in school-aged children. Treatment is usually accomplished with permethrin creme rinse, but resistance to this agent, as well as to lindane, another antipediculosis medication, has been reported. Some have advocated shaving the patient's head or applying petroleum jelly (or a similar occlusive substance) to the scalp; some dangerous home remedies include applying kerosene or insecticides to the child's scalp. One experimental treatment is the use of trimethoprim-sulfamethoxazole (TMP-SMX) plus 1 percent permethrin. Hipolito and colleagues conducted this study to compare the efficacy of single versus combination therapy in the treatment of head lice.

Children were included in the study if they were two to 13 years of age, had no known sensitivity to any of the treatment medications and were determined by visual inspection to have an infestation with head lice (adult, nymphal or egg-stage lice). Parental neglect was an exclusion criterion. Children were randomized to receive either 1 percent perme-thrin (applied for 10 minutes to the hair and scalp, with reapplication after one week if needed), TMP-SMX (10 mg per kg per day in divided doses for 10 days) or permethrin plus TMP-SMX. Parents were instructed about recognition and prevention of head lice reinfestation. All participants were re-examined at two and four weeks after treatment. Presence of adult lice, nymphal stage lice or nits (not simply nits alone) constituted a treatment failure. If the two-week visit still showed evidence of infestation, retreatment with the original regimen occurred.

There were 115 children who participated in the study. The success rate in the permethrin group was 79.5 percent, compared with 83 percent in the TMP-SMX group and 95 percent in the combined treatment group. At the four-week follow-up visit, the rates were 72 percent, 78 percent and 92.5 percent, respectively. No major side effects were noted; three children discontinued treatment because of a rash that appeared to be related to administration of TMP-SMX.

The authors conclude that combination treatment with 1 percent permethrin creme rinse and a 10-day course of TMP-SMX is an effective treatment for head lice infestation. This therapy should be given only to patients who have previously failed treatment or in whom resistance is suspected. It should not be considered first-line treatment.