Abstract

BackgroundMalathion 0.5% has been the most prescribed pediculicide in the United Kingdom for around 10 years, and is widely used in Europe and North America. Anecdotal reports suggest malathion treatments are less effective than formerly, but this has not been confirmed clinically. This study was designed to determine whether malathion is still effective and if 4% dimeticone lotion is a more effective treatment for head louse infestation.Methodology/Principal FindingsWe designed this study as an assessor blinded, randomised, controlled, parallel group trial involving 58 children and 15 adults with active head louse infestation. Each participant received two applications 7 days apart of either 4% dimeticone lotion, applied for 8 hours or overnight, or 0.5% malathion liquid applied for 12 hours or overnight. All treatment and check-up visits were conducted in participants' homes. Cure of infestation was defined as no evidence of head lice after the second treatment. Some people were found free from lice but later reinfested. Worst case, intention to treat, analysis found dimeticone was significantly more effective than malathion, with 30/43 (69.8%) participants cured using dimeticone compared with 10/30 (33.3%) using malathion (p<0.01, difference 36.4%, 95% confidence interval 14.7% to 58.2%). Per protocol analysis showed cure rates of 30/39 (76.9%) and 10/29 (34.5%) respectively. Irritant reactions were observed in only two participants, both treated with malathion.Conclusions/SignificanceWe concluded that, although malathion liquid is still effective for some people, dimeticone lotion offers a significantly more effective alternative treatment for most people.Trial RegistrationControlled-Trials.com ISRCTN47755726

Highlights

  • In a previous study [1] we demonstrated 4% dimeticone lotion was effective to eliminate head louse infestation from 70% of cases and equivalent in activity to 0.5% phenothrin liquid

  • We have been aware that resistance to malathion in head lice has been spreading in the UK since it was first identified from Brighton in 1995

  • The study was designed to compare the efficacy of 4% dimeticone lotion with 0.5% malathion liquid with sufficient power to be able to determine if activity against head lice of either product was superior to the other

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Summary

Introduction

In a previous study [1] we demonstrated 4% dimeticone lotion was effective to eliminate head louse infestation from 70% of cases and equivalent in activity to 0.5% phenothrin liquid. We have performed a controlled trial, analysed by intention to treat, comparing the efficacy of two applications 7 days apart of either 4% dimeticone lotion or 0.5% malathion liquid. This study was designed to determine whether malathion is still effective and if 4% dimeticone lotion is a more effective treatment for head louse infestation. Intention to treat, analysis found dimeticone was significantly more effective than malathion, with 30/43 (69.8%) participants cured using dimeticone compared with 10/30 (33.3%) using malathion (p,0.01, difference 36.4%, 95% confidence interval 14.7% to 58.2%).

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