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Pediatrics. 2001 Mar;107(3):E30.

Head lice infestation: single drug versus combination therapy with one percent permethrin and trimethoprim/sulfamethoxazole.

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Department of Pediatrics, University of California, Davis, California 95616, USA.



Head lice infestation (HLI) is a vexing problem for pediatricians and families because lice are becoming resistant to approved antipediculosis agents.


This study compared the efficacy of 3 different treatments for HLI and determined whether combination therapy reduced treatment failures.


A randomized, clinical trial performed in 3 private practices.


The population was children ranging in age from 2 to 13 years.


HLI was diagnosed by direct inspection of the hair and scalp. Children were assigned to 1 of 3 groups: 1) 1% permethrin creme rinse (1% PER; n = 39); 2) oral administration of trimethoprim/sulfamethoxazole (TMP/SMX; n = 36); and 3) a combination of 1% PER and TMP/SMX (n = 40). Follow-up visits were done 2 and 4 weeks later, and parents or caregivers of those who did not return were interviewed by telephone. If HLI was present at the 2-week follow-up, the child was retreated per their protocol. We defined successful treatment as the absence of adult lice and nymphal stage or eggs (nits). The presence of nits alone was not considered a treatment failure.


At the 2-week follow-up visit, successful treatment for groups 1, 2, and 3 was 79.5%, 83%, and 95%, respectively. At the 4-week follow-up, successful treatment was 72%, 78%, and 92.5% for groups 1, 2, and 3, respectively. The absolute risk reduction for recurrence comparing group 1 versus group 2 was 6%, group 2 versus group 3 was 14%, and group 1 versus group 3 was 20%. No major adverse complications were seen in any treatment group.


Our findings indicate that a combination of 1% PER and TMP/SMX is an effective alternative therapy for HLI. We recommend that the dual therapy with 1% PER and oral TMP/SMX be used and reserved in cases of multiple treatment failures or suspected cases of lice-related resistance to therapy.

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