Pyrethrins combined with piperonyl butoxide (RID) vs 1% permethrin (NIX) in the treatment of head lice

In a randomized controlled trial, 58 subjects were treated for Pediculus humanus var capitis with either pyrethrins combined with piperonyl butoxide (RID, Pfizer Inc, New York) or 1% permethrin (NIX, Burroughs Wellcome Co, Research Triangle Park, NC); 31 subjects received RID and 27 subjects received NIX. Both products were applied according to manufacturer's directions so that NIX was applied only on the first visit and RID was applied on the first visit and again seven days later. After each treatment with a pediculicide, the comb supplied by the manufacturer was used to remove nits. Seven days after the initial visit, NIX was determined to be significantly better than RID for eradicating the lice infestation. Of the 27 subjects receiving NIX, 26 were live free vs 14 of the 31 RID-treated subjects. At day 14, there was no statistically significant difference in the treatments (27 of 27 NIX-treated vs 29 of 31 RID-treated subjects were lice free). The RID comb was superior to the NIX comb for nit removal. Both treatments were effective and well tolerated, and no subject experienced adverse reactions.