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Treatment of head louse infestation with 4%
dimeticone lotion: randomised controlled
equivalence trial
Ian F Burgess, Christine M Brown and Peter N Lee 2005;330;1423-; originally published online 10 Jun 2005; BMJdoi:10.1136/bmj.38497.506481.8F Updated information and services can be found at: References
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Treatment of head louse infestation with 4% dimeticone lotion:
randomised controlled equivalence trial
Ian F Burgess, Christine M Brown, Peter N Lee
Abstract
eight hours or overnight on the basis of a phase II clinical studythat compared two 20 minute treatments a week apart with two Objective To evaluate the efficacy and safety of 4% dimeticone
treatments for eight hours or overnight. In 40 randomised lotion for treatment of head louse infestation.
participants (35 children), the 20 minute regimen cured 12 of 20 Design Randomised controlled equivalence trial.
(60%) and the eight hours or overnight treatment cured 18 of 20 Setting Community, with home visits.
(90%), giving a difference of − 30% (95% confidence interval Participants 214 young people aged 4 to 18 years and 39
adults with active head louse infestation.
We compared the efficacy of two applications seven days Interventions Two applications seven days apart of either 4.0%
apart of either 4.0% dimeticone lotion or 0.5% d-phenothrin liq- dimeticone lotion, applied for eight hours or overnight, or 0.5% uid. Phenothrin is currently the most widely used pediculicide in phenothrin liquid, applied for 12 hours or overnight.
the United Kingdom, and we selected the liquid because its Outcome measures Cure of infestation (no evidence of head
physical form and dosage is most similar to that of dimeticone lice after second treatment) or reinfestation after cure.
lotion (it is applied for 12 hours or overnight) and it is safe for Results Cure or reinfestation after cure occurred in 89 of 127
(70%) participants treated with dimeticone and 94 of 125 (75%)treated with phenothrin (difference − 5%, 95% confidenceinterval − 16% to 6%). Per protocol analysis showed that 84 of Participants and methods
121 (69%) participants were cured with dimeticone and 90 of We recruited participants by advertising through local newspa- 116 (78%) were cured with phenothrin. Irritant reactions pers and radio. Those families who telephoned the study coordi- occurred significantly less with dimeticone (3/127, 2%) than nator received an information booklet by post. Those who with phenothrin (11/125, 9%; difference − 6%, − 12% to − 1%).
wished to enrol telephoned the study coordinator to arrange a Per protocol this was 3 of 121 (3%) participants treated with home visit. Trained investigators visited, usually within 24 hours, dimeticone and 10 of 116 (9%) treated with phenothrin and followed a standard protocol to examine participants for (difference − 6%, − 12% to − 0.3%).
head lice by using a plastic detection comb. If lice were found and Conclusion Dimeticone lotion cures head louse infestation.
the participant was eligible, he or she was invited to join the Dimeticone seems less irritant than existing treatments and has study. A signed, witnessed consent and assent procedure was fol- a physical action on lice that should not be affected by lowed. Other household members were offered examination and resistance to neurotoxic insecticides.
invited to join if eligible. Treatments and assessments werecarried out in the participant’s home. Ineligible household Introduction
Recently, most Western countries have encouraged physical methods to treat head louse infestation, either alone or as a com- Our study was single blinded because the products looked suffi- ponent of conventional insecticidal treatments.1 2 The common- ciently different to preclude double blinding.
est method used in the United Kingdom is wet combing with Participants provided baseline data on age, sex, characteris- conditioner, known as “bug busting” (Community Hygiene Con- tics of their hair, and previous use of pediculicides. We chose the cern, London). Existing evidence suggests that this method is of lower age limit of four years as children of this age understand low effectiveness,3–5 which, combined with treatment failure explanations and can assent to procedures; we had no upper age attributed to insecticide resistance, has resulted in an increased prevalence of lice in most communities since 1995.6–8 We excluded participants who were pregnant, breast feeding, Dimeticone lotion is a new product, with no conventional sensitive to phenothrin or chrysanthemums, or had a chronic insecticide activity. It contains 4% long chain linear silicone scalp disorder,9 as well as those who had used a pediculicide (dimeticone) in a volatile silicone base (cyclomethicone). Both within the previous two weeks or had recently used bleaches, compounds are used extensively in cosmetics and toiletries, and dyes, or permanent wave products. We also excluded anyone tak- a shorter chain dimeticone is used as an anti-flatulent for infant ing trimethoprim or cotrimoxazole at evaluation or during the colic. Dimeticone is a clear, odourless fluid, which is applied in previous four weeks or who had participated in another clinical the same way as other lotions for head lice infestation, by coating the scalp and full length of the hair. The product dries by evapo- Participants were randomised using a computer generated ration of the cyclomethicone solvent. We selected application for list in balanced blocks of 10. Treatment allocation was by BMJ Online First bmj.com
numbered sealed envelopes issued in batches of 10. A duplicateset was made in the event individual code breaking was required.
At enrolment, participants were allocated treatment by the next available number held by the investigator. As randomisation was by individual, household members could receive different treat- Dimeticone 4% lotion was supplied in 100 ml glass bottles (Hedrin; Thornton and Ross, Huddersfield) and phenothrin0.5% liquid in 200 ml bottles (Full Marks Liquid; SSLInternational, Oldham). Both products were applied to dry hair, Allocated to receive 4.0% dimeticone (n=127) Allocated to receive 0.5% phenothrin liquid using enough to thoroughly moisten the hair and scalp. Investi- (n=126)Received treatment as allocated (n=125) gators applied the products a few drops at a time, spreading theliquid over the hair with their fingers, and working systematicallyaround the head. They then combed the hair with a normal grooming comb to spread treatment evenly and to ensure cover- age. Treatments were applied to the full hair length, as lice were observed to run down the hair shafts to escape the fluid, particu-larly when the silicone lotion was used. The lotion was left to dry naturally. The regimen was repeated seven days later.
Excluded from analysis, intention to treat (n=0) Excluded from analysis, intention to treat (n=0) Participants were provided with 30 ml bottles of non- medicated, conditioner-free shampoo. Carers were advised of the earliest time treatment should be removed—usually the next morning. They were asked not to use head louse combs or treat-ments during the study and not to divulge the treatment to assessors. Compliance with the protocol was assessed byretrospective questionnaire at each assessment.
Investigators, blinded to the treatment, carried out examina- Most participants had used insecticides, with 36 (14%) tions at follow-up using plastic head louse detection combs. Lice treated between two and four weeks previously. Fifty seven (23%) found on the hair or scalp were removed and fixed to the case had not used insecticides for more than three months and 73 record with clear tape. The lice were later examined to determine (29%) had never used an insecticide, with 69 (27%) having used their developmental stage and, if mature, their sex. Participants with lice 14 days after enrolment were supplied with 0.5% We randomly assigned 127 people to receive dimeticone and malathion lotion (Prioderm; SSL International).
126 to receive phenothrin. Overall, 248 (98%) participants (121in the phenothrin group) completed the trial (figure). Five Statistical analysis
participants from the phenothrin group withdrew: one dropped Our study was structured to detect equivalence to within 20% out before any follow-up assessments, two dropped out after the between treatment groups on the basis of 95% confidence limits first follow-up, one was given the wrong second treatment, and derived from the normal approximation to the binomial one washed the second application off early due to an adverse distribution. We assumed that success rates in the two groups event. For per protocol analysis we excluded eight participants would be 77.5%, based on current best evidence,3 10 but the (five in dimeticone group) who had complete datasets but one or design was sufficiently robust that if the true success rates proved more assessments outside the scheduled timing; and three (one lower, the power would be reduced but still remain high—for in dimeticone group) who were unavailable for the day 9 assess- example, over 80% power for 70% true success rates. For 90% power the sample size required for each group was determined The groups were similar in age, sex, intensity of infestation, as 114; the sample size allowed for protocol violations.
and hair length, thickness, degree of curl, and dryness or greasi- We compared groups using Fisher’s exact test and the Mann- Whitney U test. Equivalence was tested on the per protocol population. The primary outcome measure was elimination of The quantity of product applied depended on the length and head lice using two applications of treatment. Cure was defined thickness of hair. The amount of dimeticone lotion used (mean as no lice after the second application, on days 9 and 14. We rec- 54.8 ml) ranged from 13 ml for close cropped hair to 161 ml for ognised a relatively high risk of reinfestation after cure. Reinfes- thick hair longer than shoulder length. The amount of tation was defined as, on days 9 or 14, no more than two adult or phenothrin liquid used ranged from 19 ml to 204 ml (mean 71.8 third instar lice removed from participants who had been free from infestation after the first treatment.
Adverse events occurred in 16 participants using dimeticone and 24 participants using phenothrin, total adverse events num-bering 18 and 31, respectively. No difference was seen between groups in number of adverse events (seven participants had Our study was carried out between June and November 2003.
multiple events), severity of adverse events (15 participants had Overall, 214 young people aged 4 to 18 years and 39 adults moderate or severe events), relation to study treatments (10 par- agreed to take part. Duration of infestation before the study var- ticipants had events probably related to treatment), or action ied widely. Nineteen (8%) participants had had infestations diag- taken (only one participant had treatment interrupted for an nosed fewer than seven days before treatment. In total, 168 of adverse event). Treatment related events included mild eye irrita- 253 infested people (66%) had had lice for more than three tions from dimeticone drips (n = 2) and itching or irritation of months, with 118 (47%) having lice continuously for more than the scalp or neck (three in dimeticone group and 11 in one year, the longest being nine years.
BMJ Online First bmj.com
Discussion
Personal characteristics of participants (intention to treat) at baseline. Valuesare numbers (percentages) unless stated otherwise Head louse infestation can be cured with two applications of 4% Dimethicone 4.0% lotion
Phenothrin 0.5% liquid
dimeticone lotion a week apart. This silicone compound is the Characteristic
group (n=127)
group (n=126)
first medical product with a formulation specifically designed for use against head lice. Participants treated with dimeticone reported a significantly lower incidence of irritant adverse events.
Our study followed closely the methodological criteria set out in a recent Cochrane review.9 Carrying out our study in par- ticipants’ homes ensured the highest level of follow-up and reduced the drop-out rate. The exception to Cochrane criteria was in accepting participants who had used an insecticide prod- Details of hair
uct within two weeks of the study rather than four weeks. A good precedent for this, however, comes from a study that found out- come was not affected by insecticide use two weeks previously.3 Unlike that study, we were unable to undertake random sampling of the population by screening in schools, and some participants acknowledged difficulties in curing louse infesta- tions. We found no evidence that recruitment by advertising selected a biased population who wanted to eliminate head lice by intensive insecticide treatment, as half the participants had either never used insecticides or had not used one for over three months. This may explain why we encountered little evidence for insecticide resistance through treatment failure with phenothrin, unlike recent studies in which participants were referred by gen- eral practices.5 11 The posology and formulation excipients of phenothrin liquid, however, probably contribute towards activity to overcome low levels of resistance.12 Overall, the efficacy for both products was comparable to that found for malathion lotions applied by parents in North Wales in 1999 and the inves- *Many comb strokes needed to find one louse.
tigator led study of permethrin in the United States, although the †Several lice found with first comb stroke.
‡Not recorded for one participant in phenothrin group.
latter, as an efficacy study may not represent consumer use.3 10 Our method of finding head lice by dry combing with a plas- tic detection comb is similar to that used by another study.13 Our At follow-up examinations, cures were identified in 83 team is experienced in the technique. Consequently, we believe participants in the dimeticone group and 87 in the phenothrin all treatment failures were identified and any potential bias due group, with reinfestation after cure in six participants in the to under-reporting was eliminated. The frequency of follow-up dimeticone group and seven in the phenothrin group. These enabled us to identify differences between treatments, and represented positive outcomes of, respectively, 89 of 127 (70%) removal of some, but not all, lice ensured diagnostic sensitivity and 94 of 125 (75%), with a difference of − 5% (95% confidence interval − 16% to 6%). Positive outcomes in the per protocol This is the first randomised controlled trial of an insecticide- population were 84 of 121 (69%) for dimeticone and 90 of 116 free treatment that does not require physical methods to support (78%) for phenothrin, with a difference of − 8% ( − 19% to 3%).
its activity. Studies in vitro found dimeticone irreversibly The products were equivalent to within 20%, on the basis of immobilised lice within five minutes of application and indicate either the intention to treat or per protocol populations.
that it acts against head lice by coating the insects and thus Before treatment, 33 (13%) participants had heavy louse disrupting their ability to manage water. The current treatment infestations, 110 (44%) medium infestations, and 110 (44%) light problems caused by resistance to neuroactive insecticides willnot affect this product and it should be acceptable to people infestations. A heavy infestation was defined as several lice found reluctant to use insecticides on safety grounds. Its efficacy, lack of with the first comb stroke and a light infestation as many comb odour, and relative ease of use make 4% dimeticone lotion a strokes needed to find one louse. Cure, or reinfestation after viable alternative to conventional treatments, especially for peo- cure, was influenced by intensity of infestation, occurring in 13 ple who find combing laborious or impractical. Most participants (39%) cases of heavy infestations, 78 (71%) of medium had used combing extensively, often in combination with other infestations, and 92 (84%) of light infestations. Twenty eight par- products, but two thirds of participants had not succeeded, ticipants had more than 20 lice on either day 2 or day 6. Five of merely limiting the number of lice. Half had had head lice con- these had more than 20 lice removed on both days, with more tinuously for over a year, which is a clear indication that current newly hatched nymphs found on day 6 (mean 250 insects; range 81-823 insects) than on day 2 (74; 24-151). We found no differ- Products used in this study worked well to kill lice, even when ence in success between the treatments related to intensity of a cure was not achieved. Unlike phenothrin, however, dimeticone is not absorbed transdermally and could be used more than Treatments did not significantly differ at any time in the per- twice to effect a cure. We found that parents who used centage of participants with lice or the total number of lice phenothrin liquid on family members excluded from the study were sometimes less successful than investigators treating otherhousehold members, indicating that failure to cure may not be BMJ Online First bmj.com
Cooper entered the data for statistical analysis and John Fry provided What is already known on this topic
statistical assistance.
Funding: Kerris Pharmaceuticals, Jersey, which had no role in the design, Head louse infestation is widespread in children, and its execution, or interpretation of the study.
prevalence has increased since the early 1990s Competing interests: IFB has been a consultant to various makers of phar-maceutical products, alternative therapies, and combs for treating louse Treatment with insecticides may be affected by resistance, infestations. PNL has analysed similar studies for other pharmaceutical and combing has become more common as a treatment Ethical approval: Ethical approval for this study was granted by Cambridgeresearch ethics committee, and issues related to the locality were approvedby Peterborough and Fenland and Huntingdon local research ethics com- Evidence from randomised controlled trials for any form of mittees. This clinical trial was monitored and audited by Covance.
What this study adds
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irrespective of which treatment was used. The amount of product 10 Meinking TL, Clineschmidt CM, Chen C, Kolber MA, Tipping RW. An observer-blinded study of 1% permethrin crème rinse with and without adjunctive used for each application of phenothrin liquid was, mostly, combing in patients with head lice. J Pediatr 2002;141:665-70.
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11 Hill N, Moor G, Cameron MM, Butlin A, Preston M. Williamson MS. A single blind, randomised controlled trial comparing the bug buster kit with over the counter insec- Consequently, under-dosing is probably widespread in the com- ticide treatments for head lice in the UK. BMJ 2005;(in press).
munity, a problem dealt with by the 100 ml bottle used for 4% 12 Burgess IF. Dermatopharmacology of ectoparasitics and insect repellents. Dermatophar- macology of topical preparations. ed. In: B Gabard, P Elsner, C Surber, P Treffel, eds. Ber- dimeticone lotion. Better instructions for use and improved information at the primary care level could improve success.
13 Mumcuoglu KY, Friger M, Ioffe-Uspensky I, Ben-Ishai F, Miller J. Louse comb versus direct visual examination for the diagnosis of head louse infestations. Pediatr Dermatol Contributors: IFB conceived and designed the study, interpreted the data, wrote the paper, and contributed to the execution of the study. He will act as guarantor for the paper. CMB conceived, designed, and coordinated the study, was responsible for screening, treatments and assessments,interpreted the data, and helped write the paper. PNL was responsible forthe randomisation process and statistical analyses, and helped interpret the Insect Research and Development, Shepreth, Royston SG8 6QZ findings and write the paper. Treatments and assessments were carried out by Anne Scarlett, Audrey Pepperman, Caroline Priestley, Nazma Burgess, Christine M Brown study coordinator and Matthew Southward. Kate King monitored and evaluated adverse P N Lee Statistics and Computing, Sutton, Surrey SM2 5DA events and acted as the medical contact throughout the study. Sam Shuster was the dermatological medical expert. Katharine Young and Yvonne Correspondence to: I F Burgess ian@insectresearch.com BMJ Online First bmj.com

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