© The Author • Journal compilation © Blackwell Verlag GmbH, Berlin • JDDG • 1610-0379/2010/0812 JDDG | 12˙2010 (Band 8)

JDDG; 2010 • 8:985–988 Submitted: 2.4.2010 | Accepted: 29.5.2010

Keywords• oral Ivermectin• head lice• malathion lotion

SummaryBackground: Reports of treatment failure of head lice have become increasinglycommon. Oral ivermectin has been proposed as a potential alternative for thetreatment of head lice infestation. The aim of this study was to compare theefficacy of oral ivermectin with topical malathion lotion in the treatment ofhead lice.Patients and methods: Eighty apparently healthy children with head lice infes-tation were randomly assigned to 2 groups, with 40 patients in each. The firstgroup received oral ivermectin as a single dose of 200 µg /kg and the secondgroup received single topical application of malathion lotion 0.5 %. Follow upvisits were done at days 8, 15 and 29. A second dose of either drug was givenat day 8 in case of treatment failure.Results: After a single dose, complete cure was achieved in 77.5 % and 87.5 %of ivermectin and malathion groups respectively. After the second dose fornonresponders, the cure rate increased to 92.5 % in the ivermectin group and95 % in the malathion group. No major adverse effects were observed in eithergroup. Conclusions: Oral ivermectin is a promising effective approach for the treatmentof head lice and could be an ideal substitute for conventional pediculicides.

Oral ivermectin for head lice: a comparison with 0.5 % topical malathion lotionAhmad NofalDermatology Department, Faculty of Medicine, Zagazig University, Zagazig, Egypt

IntroductionInfestation with head lice is a worldwideproblem of public health concern. It iscaused by the highly host-specific insectPediculus humanus var capitis that liveson human skin and can survive only onhuman blood [1]. With the exception ofcommon cold, head lice affect moreschool-age children than all other com-municable childhood diseases combined[2].Head lice treatment involves a three di-mensional approach that includes pedi-culicides, mechanical removal and envi-ronmental measures to prevent furthertransmission and reinfestation. First linetopical agents are available over thecounter and are devoid of major toxici-ties. These products contain eitherpyrethrins combined with piperonyl bu-

toxide or the more potent syntheticpyrethroid, permethrin 1 % [3–6]. Alter-native prescriptive agents include: per-methrin 5 % which is applied overnightunder a shower cap [3], lindane (gammabenzene hexachloride 1 %) which hadbeen a popular treatment but is nolonger the preferred one because of con-cerns about its neurotoxicity [7], andmalathion 0.5 % which is considered bysome investigators to be the first-line op-tion, particularly in the present era ofpermethrin and lindane resistance inhead lice [8].During recent years, an increase in thehead lice treatment failure has been re-ported in different areas of the world.These failures are in many cases the re-sult of reinfestation or lack of adherenceto the treatment protocols. However,

head lice resistance to conventional pedi-culicides has been increasingly observed[6, 9]. Oral ivermectin has been pro-posed by many authors as a potential al-ternative in the treatment of head lice,especially for cases resistant to conven-tional therapy [3–6, 9–12].Ivermectin is an antihelmintic agentstructurally similar to the macrolide an-tibiotics, but without antibacterial activ-ity. It has been used to treat a variety ofinfestations in animals. In humans, iver-mectin has been proved effective in thetreatment of onchocerciasis, loiasis,strongyloidiasis, bancroftian filariasis,cutaneous larva migrans and scabies [3,13, 14]. The safety of ivermectin hasbeen demonstrated during its extensiveuse against nematodes where the adverseeffects were rare and minor [13]. Safety

DOI: 10.1111/j.1610-0387.2010.07487.x Original Article 985

in pregnant and lactating women and inchildren weighting less than 15 kg hasnot been established [9].The aim of this study was to compare theefficacy of oral ivermectin with topicalmalathion 0.5 %, a pediculicide withwell established efficacy, in the treatmentof head lice.

Patients and methodsPatient enrollmentThe study included 80 apparentlyhealthy children with pediculosis capitiswho were attending the outpatient clinicof Dermatology Department at ZagazigUniversity, Egypt. A written informedconsent was obtained from the parents ofall patients before enrollment. Patientsweighing less than 15 kg or less than 5 years of age were not enrolled into thestudy because of concerns about safety ofivermectin in this subset of patients [9].Because no residual effect of any pedi-culicide lasts for more than 2 weeks [3],patients who received treatment forpediculosis capitis in the previous 2 weekswere also excluded from the study. Diag-nosis of active infestation was based onthe presence of live moving lice only.This was made by combing the dry hairwith a fine-toothed detection comb, aspreviously described [15]. The severity of infestation was evaluatedat the time of inclusion; + (1–5 movinglice), ++ (6–10), +++ (11–20) and ++++(> 20) [16]. Demographic data and base-line clinical parameters were obtained forall patients at the start of the study. Pa-tients with evidence of secondary bacter-ial infection were treated with antibioticsbefore being enrolled into the study.Trimethoprim-sulfamethoxazole was notemployed as it has been shown to be ef-fective against head lice [17].

Drug administrationOnce the diagnosis was made, the patients were randomly assigned to oneof 2 groups. The first group (n = 40) re-ceived ivermectin as a supervised singleoral dose of 200 µg /kg body weight, andthe second group received malathion0.5 % in a lotion form. The patientswere instructed to use malathion on adry hair, to leave it for 8–12 hours and tokeep the lotion away from flames andlighted object. Family contacts were nottreated for head lice. Adjunctive use ofnit removal combs and other topical ororal pediculicides were not allowed dur-

ing the study period. Parents were askedto treat sheets, pillow cases, clothes, hatsand other fomites with an appropriatepediculicidal powder to prevent re-infes-tation.

Evaluation and follow upAll patients were examined for the pres-ence of live lice and any side effects atday 8. A second dose of either drug wasgiven in case of treatment failure, whichwas defined as the presence of live mov-ing lice. Re-examination was done at day15 to evaluate the efficacy and side ef-fects after the second dose, and at day 29to detect re-infestation.

Statistical analysisData were entered, checked and analyzedby means of the SPSS package. Datawere expressed as number and percent-age, and Chi-square test was used as ap-propriate. P-values < 0.05 were consid-ered significant.

ResultsA total of 80 patients were studied; 40 ineach group. Their ages ranged from 6–14years. There was no significant difference(p > 0.05) between the study groups inthe baseline characteristics, including thedemographic data and the clinical pa-

rameters (Table 1). On follow up at day8, after a single dose, 31 patients(77.5 %) were cured in the ivermectingroup, and 35 patients (87.5 %) werecured in the malathion group (95 %confidence interval 0.92–138, p > 0.05)(Table 2). By day 15, after giving a sec-ond dose for the nonresponders, thenumber of the cured patients increasedto 37 (92.5 %) in the ivermectin groupand to 38 (95 %) in the malathion group(95 % confidence interval 0.92–1.15,p > 0.05). By day 29, the therapeutic re-sponse decreased in both groups. Sevenpatients were reinfested and 30 patients(75 %) were still cured in the ivermectingroup, while 6 patients were reinfestedand 32 patients (80 %) were still cured inthe malathion group (95 % confidenceinterval 0.84–1.35, p > 0.05). No majoradverse reactions were reported in bothgroups. Two patients in the ivermectingroup experienced a transient increase ofpruritus 24 hours after the first dose,while stinging of the skin and eye irrita-tion were observed in 3 patients aftertopical application of malathion.

DiscussionInfestation with head lice has affectedmankind since antiquity. Although theseobligate ectoparasites of human beings

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JDDG | 12˙2010 (Band 8) © The Author • Journal compilation © Blackwell Verlag GmbH, Berlin • JDDG • 1610-0379/2010/0812

Table 1: Baseline characteristics of the patients.

Clinical parameter

Ivermectin (n = 40)

Malathion (n = 40) X2 P-value

n % n %

0.23 0.63

Age distribution (y)6–1011–14

2614

65.035.0

2812

70.030.0

Sex distribution Male Female

1327

32.567.5

1129

27.572.5

0.24 0.62

Pruritus 28 70.0 31 77.5 0.58 0.44

Excoriations 15 37.5 19 47.5 0.82 0.36

Lymphadenitis 13 32.5 15 37.5 0.22 0.63

Previous infestation 14 35.0 12 30.0 0.23 0.63

Level of infestation++++++++++

21964

52.522.515.010.0

24763

60.017.515.07.5

0.460.310.000.16

0.490.571.000.69

In contrast, Youssef et al. [30] have re-ported that ivermectin 0.8 % solutionhad a lethal effect on all stages of the par-asite resulting in clearance of head licewithin 48 hours after a single topical ap-plication. These findings may be attrib-uted to the topical route of administra-tion of ivermectin which would increasesufficient duration to provide prophy-laxis against the developing nymphs[31]. A second dose of either drug was given tothe nonresponders after one week, toeradicate any newly hatched lice. By day15, two doses of ivermectin became as ef-fective as two doses of malathion(Table 2). Because ivermectin has notbeen proven to be ovicidal, and itsplasma half life is 16 hours, a single dosemay be inadequate to eradicate the dif-ferent stages of the parasite and a seconddose on day 8 is recommended in orderto kill nymphs that hatch after the initialdose [3, 6]. This could account for thehigher response to ivermectin after thesecond dose. A similar finding has alsobeen observed by many authors [3, 5,10, 11] who reported that a single oraldose of ivermectin 200 µg/kg repeated in7–10 days is effective in eradicating headlice.By day 29, the therapeutic response de-creased in both groups. This may be duea re-infestation from the non-treatedhousehold or close contacts and im-proper disinfection of the infestedclothes and bedding. Most experts rec-ommend that household members andthose in close contact with the patientshould be screened for head lice andtreated as necessary [25]. Because it wasnot possible to examine all the house-hold and close contacts of every patientto give treatment for the infested mem-bers, family or other close contacts werenot treated for pediculosis capitis in thisstudy.No major adverse effects were observedin either group. Stinging of the skin andeye irritation were observed in three patients treated with malathion. This has been reported before and could be related to the alcoholic vehicle ofmalathion lotion [26]. In the ivermectingroup, two patients experienced initialaggravation of pruritus which subsidedspontaneously within three days. A simi-lar finding has been observed by otherauthors [10, 13, 14] and could be attrib-uted to a hypersensitivity reaction

Oral ivermectin vs. malathion lotion for head lice Original Article 987

© The Author • Journal compilation © Blackwell Verlag GmbH, Berlin • JDDG • 1610-0379/2010/0812 JDDG | 12˙2010 (Band 8)

are not vectors of any human disease,pediculosis capitis should not be trivial-ized. It is uncomfortable, physically un-pleasant and can result in psychologicalfrustration for parents and children [18,19]. Pediculosis capitis is a major publichealth problem in Egypt, particularlyamong school children irrespective oftheir socioeconomic status [20].Clinical and parasitological resistance tohead lice was first observed in1994 [16].Since then, head lice resistance has beenoften documented [6, 9, 21, 22]. Strate-gies for treating resistant lice includeyearly rotation of available pediculicides,retrying the initial agent at a higher con-centration or for a longer applicationtime, and switching to a different prod-uct [3]. Hence, we considered it worth-while to try a new agent, oral ivermectin,for the treatment of head lice.In this study, there were no significantdifferences between the treatmentgroups in the baseline characteristics ofthe patients indicating successful ran-domization. More girls than boys tookpart in this study, reflecting the higherprevalence of head lice in girls [23].Despite the high frequency of pediculo-sis capitis among children, there is noagreement as to what constitutes an in-festation. Some studies defined an infes-tation as the presence of live lice only[24, 25], whereas others have used thepresence of either nits or lice [16, 26]. Inthe present study, infestation was definedby the presence of live lice only becausenonviable nits may persist for months af-ter successful treatment [2].In this study, a single oral dose of iver-mectin provided a cure rate of 77.5 %.This was in agreement with Bell [12]who showed an efficacy of 73 %. Similarfindings have also been reported byDunne et al. [27] and Burkhart et al.[28]. On the contrary, Glaziou et al. [10]have reported a low success rate of 23 %that may be related to the small numberof the studied patients and the different

definition of cure (complete disappear-ance of eggs and all clinical symptoms).The cure rate after a single topical appli-cation of malathion was 87.5 %. Thiswas lower than the results (95 %) re-ported by earlier studies [16, 26]. Lack ofproper application and possible resist-ance to malathion because of its wide-spread use in Egypt could account forthe lower efficacy reported in this study.This study showed that a single topicalapplication of malathion was superior toa single oral dose of ivermectin, but thedifference was statistically insignificant.Malathion, an organophosphate that in-hibits cholinesterase, is believed to act onall stages of the parasite, although it isnot 100 % ovicidal [8]. Furthermore,topical application insures maximumconcentration of the drug in the skin.These factors could explain the higherefficacy of a single topical application ofmalathion. On the other hand, Chosi-dow et al. [29] have shown that oral iver-mectin had a superior efficacy (97.1 %)as compared with topical 0.5 %malathion lotion (89.7 %). The differ-ence between these results and the pres-ent study may be attributed to the muchhigher number of the studied patients(812 vs. 80) and the higher dosage of ivermectin (400 µg/kg vs. 200 µg/kg)respectively.The lack of efficacy of a single dose ofivermectin in some patients may be dueto the lack of ovicidal action of iver-mectin [3, 27]. Ivermectin acts by block-ing the chemical transmission acrossnerve synapses that use glutamate orgamma-aminobutyric acid which are theneurotransmitters for peripheral motorfunction in lice [6]. This results in paral-ysis and death of the parasite. Becausedeveloping eggs have no central nervoussystem during the first 4 days of life, anyinsecticide, including ivermectin thatacts on the metabolism of neural tissueswould prove ineffective unless it has sig-nificant residual activity [3].

Table 2: Cure rates among the studies patients.

DayIvermectin group Malathion group

X2 P-valuen % n %

8 31 77.5 35 87.5 1.39 0.23

15 37 92.5 38 95.0 0.21 0.64

29 30 75.0 32 80.0 0.29 0.59

against the antigens of the destructedparasite. Though very rarely reported,emerging resistance to ivermectin in hu-mans has been recently observed [32].Ivermectin was administered under su-pervision at the time of diagnosis, thisrepresents an advantage that would over-come the problems of non-compliance,misuse and inadequate application asso-ciated with topical therapy, and givesivermectin an important role in the com-munity control of head lice. <<<

Conflict of interestNone.

Correspondence toAhmad Nofal, MD Dermatology DepartmentFaculty of MedicineZagazig UniversityZagazig, EgyptTel.: +20-121180819E-Mail: ahmadnofal5@hotmail.com

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988 Original Article Oral ivermectin vs. malathion lotion for head lice

JDDG | 12˙2010 (Band 8) © The Author • Journal compilation © Blackwell Verlag GmbH, Berlin • JDDG • 1610-0379/2010/0812