Efficacy and Safety of a Water-Based Head Lice Lotion: A ... · Pediculosis capitis; Pyrethrum; Silylated polyol INTRODUCTION Head lice (Pediculus humanus capitis) are hema-tophagous

ORIGINAL RESEARCH

Efficacy and Safety of a Water-Based Head Lice Lotion:A Randomized, Controlled, Investigator-Blinded,Comparative, Bicentric Study

Frank Eertmans . Bart Rossel . Lidia Serrano . Elisabeth Rivera .

Els Adriaens

Received: September 26, 2018 / Published online: November 30, 2018� The Author(s) 2018

ABSTRACT

Introduction: Silicones (e.g., dimethicone) areeffective and safe alternatives to insecticides forthe treatment of head lice. However, siliconesare lipophilic substances and do not only leavethe hair greasy but they are also difficult to washout. We have evaluated the efficacy and safetyof a potential solution to this problem: anaqueous dispersion of a novel silylated polyolthat has the same mode of action as dime-thicone (suffocation) without its negativeimpact on hair characteristics.Methods: This was a randomized, controlled,investigator-blinded, bicentric study that was

conducted at two locations in the state of Flor-ida (USA) to compare the test product (medicaldevice) to a pyrethrum-based pediculicide thatis a first-line, prescription-free treatment againsthead lice in the USA. The subjects (n = 70) wererandomly divided into two groups of 35 persons(test product group and reference productgroup), with each participant receiving twoapplications (day 0 and 7) of the product to betested, according to the instructions for use.Efficacy and safety was evaluated at distincttime points. The primary objective was toestablish a cure rate for the test product that wasbetter than 70% at study end (day 10). Estheticeffects of the test product versus dimethiconewere evaluated in a blinded, cross-over con-sumer study (n = 100).Results: At study end, the cure rate (correctedfor re-infestation) of 88.2% with the test pro-duct significantly surpassed the pre-definedtarget of 70%, and thus the superiority of thetest product versus the reference product wasconfirmed. The number of subjects cured (freeof head lice) after the first treatment wasremarkably higher with the test product thanwith the reference product (57.1 vs. 2.9%,respectively). Both products were safe and welltolerated and both showed beneficial estheticaleffects. The consumer test demonstrated thatthe test product had better washing-out prop-erties than dimethicone, as reflected by a sig-nificantly lower average rinsing time andnumber of washings required to restore the

Enhanced Digital Features To view enhanced digitalfeatures for this article go to https://doi.org/10.6084/m9.figshare.7364558.

F. Eertmans (&) � B. RosselOystershell Laboratories, Nijverheidsweg 10, 9820Merelbeke, Oost-Vlaanderen, Belgiume-mail: [email protected]

L. SerranoLice Cleanique, South Florida Family Health &Research Centers, LLC, 13500 SW 88th Street #175,Miami, FL, USA

E. RiveraLice Source Services, Inc., 6971 West Sunrise Blvd.,Suite 102, Plantation, FL 33313, USA

E. AdriaensAdriaens Consulting, Bellemdorpweg 95, 9881Bellem, Oost-Vlaanderen, Belgium

Dermatol Ther (Heidelb) (2019) 9:143–157

https://doi.org/10.1007/s13555-018-0274-x

visual aspect of the hair, especially in terms ofgreasiness.Conclusion: Aqueous dispersions of silylatedpolyols are a promising new class of pediculi-cides that combine high cure rates with optimaluser convenience (short treatment period, easywash-out with positive effect on hair quality).Trial Registration: ClinicalTrials.gov identifier,NCT03617926.Funding: Oystershell Laboratories.

Keywords: Aqueous-based; Comparative trial;Pediculosis capitis; Pyrethrum; Silylated polyol

INTRODUCTION

Head lice (Pediculus humanus capitis) are hema-tophagous ectoparasites which live on thehuman scalp. They are very contagious andtypically spread via close contact with infestedindividuals. Head lice are common and widelyspread, with highly diverging prevalence values[1, 2].

Because of increasing resistance and safetyissues [3, 4], the use of insecticides (e.g., pyre-throids) as first-line agents against head lice hasbeen largely surpassed by physically acting,substance-based medical devices that typicallycontain silicones and/or mineral oils. Thephysical mode of action of these devices iswidely accepted and relies on suffocation of theectoparasites by blocking their respiratorychannel, hereby impairing water and gasexchange. Mineral oils are also able to disruptthe epicuticular wax layer of head lice [5–8].

Such agents have a lipophilic character, andespecially high-molecular-weight silicones canaccumulate on the hair, making themdifficult towash out and therefore turning the hair greasy[9]. These negative properties have led research-ers to search for alternative, physically activecompounds that combine efficacy and optimaluser convenience in terms of treatment periodand with the lack of negative effects on hairquality. Different screening efforts have resultedin the identification of a group of synthesized,silylated polyols, which show the most interest-ing properties with respect to adulticidal andovicidal activity (100% mortality). Furthermore,

in contrast to the high-molecular-weight sili-cones, short silylated polyols have a very lowviscosity, allowing easy dispersion in viscousaqueous formulations. From an esthetical pointof view, thesemolecules are promising as they donot leave residue on the hair and do not have anegative impact on hair quality in general.

The clinical trial described here was designedand implemented to compare the efficacy,safety, and cosmetic effects of an aqueous dis-persion of a silylated polyol (Prosil) versus afirst-line, prescription-free treatment in theUSA: RID shampoo (pyrethrum-based). We alsoperformed a blinded, cross-over consumer studyto further evaluate the esthetic effects of the testproduct versus a silicone-based product (4%dimethicone).

METHODS

Clinical Study Set-Up

This randomized, controlled, investigator-blin-ded, comparative study was approved by theSchulman IRB Ethics Committee (Cincinnati,OH, USA) on 16 January 2018. The trial wasconducted according to the internationalguideline for clinical trials with pediculicides[10], in accordance with Good Clinical Practiceand with the principles of the Declaration ofHelsinki 2013. This study was registered atClinicalTrials.gov (NCT03617926).

The entire clinical study took place at twoclinical trial sites in Florida (USA) that are spe-cialized in treating people infestedwith head lice(site 1: Lice Source Services, Plantation, FL; site 2:Lice Cleanique, Miami, FL). Recruitment wasperformed by trained personnel and continuedfrom 7 March 2018 (first visit of first patient) to30th June 2018 (last visit of last patient). Patientswere recruited among infested subjects who vis-ited one of either clinic for a head lice treatment.

Inclusion and Exclusion Criteria

Inclusion and exclusion criteria were identicalto those used in the study of Wolf et al. [11].Briefly, patients ([2 years of age; male/female)

144 Dermatol Ther (Heidelb) (2019) 9:143–157

were included after head lice infestation wasconfirmed. Full scalp and hair diagnoses wereperformed by experienced clinical staff using aplastic head lice comb. First, the hair wasdetangled into three sections, and every sectionwas combed six times, beginning at the scalpand ending at the hair tips. Head lice caught bythe comb were left in the hair to avoid bias. Theseverity of the head lice infestation was classi-fied as follows: not relevant (\5 lice and/ornymphs), mild (5–9 lice and/or nymphs),moderate (10–24 lice and/or nymphs), andsevere (C 25 lice and/or nymphs).

Only patients with a mild, moderate, orsevere infestation, with at least five apparentlylive nits (based on location and visual appear-ance), and a good general condition wereincluded in the study. Exclusion criteria were:sensitivity towards ingredients; use of a pedi-culicide 1 month prior to and during the study;use of topical drugs or medication which mayinterfere with study outcome; scalp disorders;pregnancy or lactation; participation in anotherclinical trial (also taking into account a periodof 4 weeks before study start); being affiliated tothe sponsor or investigator site personnel; andnon-compliance with the protocol.

Informed Consent, Randomization,and Baseline Data

During recruitment, the clinical staff provideddetailed information on study procedures andobjectives. Following written consent by theparticipant (or his/her legal representative),each subject was randomly allocated into one oftwo groups. Baseline demographic and clinicaldata were collected. Prior to the study, a ran-domization list was built by an external statis-tician using SAS software (version 9.4; SASInstitute, Cary, NC, USA). For this purpose,block randomization with a variable block size(2–8) was used. All patients confirmed theiravailability for the 10-day duration of the study.

Blinding

Because of differences in product characteristics(color, odor, composition…), a double-blinded

study was not possible. Therefore, treatmentswere provided by unblinded study staff, whereasconsequent assessments were performed byblinded study staff (not involved in the treat-ments) to avoid any product bias.

Study Products, Dosage,and Administration

Both products were applied according to therespective instructions for use. The test product(medical device) and corresponding lice combwere supplied by Oystershell (Merelbeke, Bel-gium). The lotion is provided as a dual chamberpackaging system. Briefly, the cap contains theconcentrated silylated polyol (Prosil), which isdissolved in a lipophilic vehicle. The 100-mlplastic bottle contains the water diluent (sup-plemented with preservatives, perfume, and aviscosity modifier). Prior to use, the cap is acti-vated by pushing, hereby releasing the Prosilinto the water phase. Next, the product is sha-ken thoroughly and immediately applied ontodry hair until the hair is fully saturated. After 15(? 2) min, the hair is rinsed with warm waterand a commercial mild shampoo (Johnson’sbaby shampoo; Johnson & Johnson, NewBrunswick, NJ, USA).

The reference product, namely RID sham-poo, is commercially available in the USA. Itcontains pyrethrum extract (equivalent to0.33% pyrethrins) and piperonyl butoxide (4%),with the latter serving as activity booster. Pyre-thrum is extracted from flower heads ofChrysanthemum cinerariifolium and containspyrethrins, cinerins, and jasmolins. The extracthas neurotoxic effects and kills insects, includ-ing head lice, by acting on their central nervesystem (disruption of muscle neurotransmis-sion) [3, 12]. The clinical trial centers purchasedRID shampoo from stores as 118-ml glass bot-tles, supplemented with a lice comb.

Depending on the length of the hair, thefollowing volumes were applied to the hair(according to the instructions for use): 60 ml(short hair), 90 ml (shoulder length-hair), andcomplete bottle (mid-back hair), respectively.The product was applied evenly in dry hair overits full length, with special attention paid to the

Dermatol Ther (Heidelb) (2019) 9:143–157 145

hair and scalp. After 10 (? 2) min, warm waterwas applied, and the product was rinsed outthoroughly.

Patients received two treatments, a firstapplication at visit 1 (day 0) and a second atvisit 3 (day 7), according to the instructions foruse of both products.

Efficacy Evaluation

Infestation degree in both treatment groups wasdiagnosed using a plastic head lice comb.Assessments were made at the following timepoints: day 0 (visit 1), 24 h post treatment (visit2), day 7 post treatment (prior to second treat-ment; visit 3), and day 10 post treatment(visit4).

The primary objective of this study was todemonstrate that the cure rate of the test pro-duct surpassed 70% at day 10. The cure rate isthe proportion of patients without any livinglice, corrected for re-infestation and was definedas (1) no adult lice or third-stage nymphs pre-sent following the first treatment, and (2) nomore than two adult lice or third-stage nymphsfound by combing on day 10 [13].

The secondary efficacy objectives were toshow (1) that the cure rate at the end of day 10(corrected for re-infestation) for the referenceproduct surpassed 70%, and (2) that the testproduct had a cure rate superior to that of thereference product. In the case that superioritycould not be shown, the secondary efficacyobjectives were to demonstrate that the testproduct was non-inferior to the reference pro-duct, using a non-inferiority margin of 7.5%.More detailed information is provided in theStatistical Analyses section.

Sample Size Calculation

Sample size calculation relied on previousunpublished and published clinical data [11]. Apre-defined limit of 70% was chosen, based onthe highest cure rate reported to date, from aclinical trial with a pyrethroid-based pediculi-cide [14]. This limit was assumed to be theminimal acceptable cure rate. A sample size of30 was needed for a one-sample Chi-square test,

comparing a cure rate of 95% with a fixed limitof 70% (two-sided test; alpha level of 0.05;power 80%). For the control group, an identicalsample size was used.

Assuming a 10% drop-out and a 5% re-in-festation rate, the sample size was multiplied by1.1 9 1.05, resulting in 35 cases per group(n = 70 in total).

Safety Evaluation

Assessment of safety, tolerability, and accep-tance of both products were some of the sec-ondary objectives. Such assessments wereperformed before and after the first (day 0) andsecond treatment (day 7), respectively. A finalexamination was done at study end (day 10) toassess local tolerability, as reflected by thepresence of burning, pruritus, and paresthesia.Study staff evaluated skin condition (secondaryinfection, skin redness, excoriation) and ocularirritation on days 0, 1, 7, and 10, respectively.Global tolerability was evaluated by the clinicalstaff at study end.

Esthetic Questionnaire

Following application of the first and secondtreatment, an aesthetic questionnaire wascompleted by the subjects on days 0 and 7,respectively. The questions related to dryness,shininess, greasiness, and volume of the hair;feeling of the hair and scalp; and the condi-tioning effect of the treatment. The followingscores were assigned: (a) strongly agree,(b) agree, (c) disagree, and (d) strongly disagree.

Consumer Study

The blinded, cross-over study was designed andimplemented by VG Sensory (Deinze, Belgium),a firm which is specialized in conducting con-sumer tests and evaluating sensory properties ofcosmetics, food products, among others. Thestudy started on 9 August 2018 and finished on25 September 2018. Subjects (n = 100) wererecruited from a database of people with home

146 Dermatol Ther (Heidelb) (2019) 9:143–157

experience in the use of head lice products. Inthis study, the test product was compared to acommercially available 4% dimethicone lotion.People were instructed to use the productaccording to the respective leaflet. A commer-cially available mild shampoo was used to washout the product (same for both treatments). Atstudy start, 50 subjects started with one testproduct and the remaining 50 with the other.Following treatment, a ‘‘wash-out’’ period of14 days had to be respected before the partici-pants started on the other treatment. Differentparameters were recorded in a diary: timerequired to wash out the product; the numberof washings required to restore hair character-istics; and the volume of shampoo used. Allsubjects completed a questionnaire to score theesthetic aspects of the hair, including greasi-ness, shininess, feel, and of the scalp, amongothers.

In vitro Adulticidal Testsand Microscopical Analyses

Living head lice were collected from a school inthe direct environment of Oystershell Labora-tories and immediately used in an in vitroadulticidal test. Briefly, all stages of viable headlice (n = 10) were transferred to a self-made‘‘arena’’, which was an enclosed circle of nylongauze. Next, head lice were treated with 2 ml ofthe test product, namely, 4% dimethiconelotion (positive control), or with 2 ml tepidwater (negative control) for 15 min. Followingincubation, lice were rinsed with a 5% dilutionof a commercial shampoo and water. Survivalwas assessed at distinct time points for a periodof up to 3 h. Treated lice (all products) werethen transferred to the LIMID laboratory(University of Antwerp, Belgium) for micro-scopical analysis to evaluate penetration of testproduct in the respiratory tract. This methodwas based on experiments performed by Rich-ling [15]. Imaging of the lice was performedwith a Zeiss Stemi SV11 stereomicroscope (CarlZeis NV, Zaventem, Belgium), equipped with anOlympus DP70 CCD Camera (Olympus,Antwerp, Belgium).

Statistical Analyses

Clinical trial data were analyzed by an inde-pendent statistician according to the Interna-tional Conference on Harmonization (ICH) E9Note for Guidance on Statistical Principles forClinical Trials [16].

Efficacy analyses were performed on theintention-to-treat (ITT) population. The latterincluded all subjects who were recruited andrandomized in the study, with baseline valuesof the primary endpoint, and at least one fol-low-up visit for the efficacy parameters. A 5%level of significance level was applied foranalyses.

The cure rate (p) corresponds to the propor-tion of patients who were cured at day 10among all patients that received any treatmentat day 0. The aim of this study was to establishsuperiority for the cure rate of the test product(pT) versus a pre-defined limit of 70% (see alsosection Sample size). The following nullhypothesis was tested: H0, prim: pT - pR = 0 andHa: pT - pR[ 15%, where pR is the cure rate ofthe reference product. The Chi-square test ofindependence was used to test the nullhypothesis. If superiority could not be proven,non-inferiority would be evaluated. Evaluationof non-inferiority is allowed if a non-inferioritymargin has been predefined, and no correctionwere made in terms of multiplicity [17]. As non-inferiority margin (d), a 7.5% worse cure ratewas seen as being clinically not relevant. In thepresent clinical trial, this analysis was not rele-vant as results clearly confirmed superiority ofthe test product.

The Chi-square test for independence wasused to compare the cure rate after correctionfor re-infestation on day 10.

All descriptive and statistical analyses wereperformed in R version 3.3.4. (R developmentcore team 2017) [18]. A p value of\0.05 wasconsidered to be statistical significant. Noimputation of missing data was performed.

For the consumer study, continuous datawere summarized by their mean, standarddeviation (SD), minimum, median, and maxi-mum. Categorical data were summarized byfrequencies and percentages. Fizz SensoryAnalysis software (Biosystemes Analysis,

Dermatol Ther (Heidelb) (2019) 9:143–157 147

Couternon, France) was used to perform analy-sis of variance tests. For time measurement data,a Mann–Whitney test was used. All statisticaltests were performed at the 5% level ofsignificance.

RESULTS

Baseline Data Clinical Trial

Study data were collected between 7 March2018 and 30 June 2018. In total, 70 subjectswere randomized into two treatment groups,namely, the test product group (32 females, 3males) and the reference product group (33females, 2 males). The average age of the par-ticipants was 14.2 ± 11.7 (± SD) years, with ageranging from 2 to 50 years. All patients com-pleted the study according to the protocol andwere included into the ITT population.A CONSORT flow chart is shown in Fig. 1. Asummary of demographic and clinical charac-teristics is presented in Table 1.

Forty patients (n = 20 in both treatmentgroups) were classified as having a mild infes-tation of head lice, and 21 patients were asses-sed as having a moderate infestation (testproduct group, n = 8; reference group, n = 13).Compared to the reference product group, moresubjects in the test product group suffered froma severe infestation (n = 7 vs. n = 2,respectively).

Before treatment (visit 0), the average num-ber of adult live lice per subject was 6.3 ± 7.2(range 0–40). The average number of adult liceand the distribution of nymphs per stage dif-fered slightly between treatment arms.

The number of subjects with short hair wascomparable in both groups (test product groupn = 3; reference product group n = 4). Withrespect to hair length and treatment for headlice infestation, there were more subjects in thereference group (n = 16) with medium long hair(shoulder length) treated for head lice than inthe test product group (n = 12), while in con-trast, there were more subjects in the test pro-duct group (n = 20) with long hair (mid-back)treated for head lice infestation than in the

Fig. 1 CONSORT flow chart (intention-to-treat population)

148 Dermatol Ther (Heidelb) (2019) 9:143–157

reference group (n = 15). Regarding hair curli-ness and thickness, no important differenceswere observed between both treatment groups.The data are summarized in Table 1.

Efficacy Results

At study end (day 10), only five of 35 subjectswere infested in the test product group (curerate 85.7%). One subject was assessed to be a re-infestation, yielding a cure rate, corrected for re-infestation, of 88.2% (30/34; 95% confidenceinterval [CI] 72.5–96.7%). At study end, 22patients in the reference product group werenot lice-free (cure rate 37.1%). Three subjectswere classified as a re-infestation, yielding a curerate, corrected for re-infestation, of 40.6% (13/32; 95% CI 23.7–59.4%). These data demon-strate that the primary objective (cure rate [70%) was only realized for the test product(p = 0.023). With a difference between curerates of 47.6% (95% CI 27.4–67.8%; v2: 16.46,p\0.001), superiority of the test product versusreference product was statistically established.

For all evaluation visits, cure rates wereremarkably higher for the test product than forthe reference product. Twenty-four hours fol-lowing initial treatment, 85.7% (30/35) and60% (21/35) of the subjects were lice-free in thetest group and reference group, respectively.Prior to the second treatment, there was a sig-nificant advantage of 40% for the test product:51.4% of the subjects in the test product groupwere lice-free versus 11.4% in the referenceproduct group.

After the first treatment, the number ofsubjects who remained lice-free until study endwas 57.1% (20/35) in the test product group and2.9% (1/35) in the reference product group. Theresults are shown in Table 2.

Satisfaction with Esthetical Effect

In the test product group, 91–100% of the sub-jects responded positively to all questions,whereas no subjects strongly disagreed. Briefly,after the first treatment, 6% of the subjects inthis group disagreed with the statement ‘‘Hairnot too dry’’; after the second treatment, only3% disagreed. Identical results were reportedregarding the conditioning effect of the prod-uct. Regarding the statements on shininess(Shininess is good) and volume of the hair(Volume is good), 3% of the subjects in the test

Table 1 Baseline characteristics of participants

Baseline characteristics Treatment groups (n = 35 ineach group)

Testproduct

Referenceproduct

Age (years)

Average ± SD 15.3 ± 12.3 13.1 ± 10.9

Minimum/median/

maximum

3/12/50 2/10/44

Sex

Male, n (%) 3 (8.6%) 2 (5.7%)

Female, n (%) 32 (91.4%) 33 (94.3%)

Severity infestation

Mild 20 (57.1%) 20 (57.1%)

Moderate 8 (22.9%) 13 (37.1%)

Heavy 7 (20%) 2 (5.7%)

Hair length

Short 3 (8.6%) 4 (11.4%)

Medium 12 (34.3%) 16 (45.7%)

Long 20 (57.1%) 15 (42.9%)

Hair curliness

Straight 8 (22.9%) 12 (34.3%)

Wavy 23 (65.7%) 16 (45.7%)

Curly 4 (11.4%) 7 (20.0%)

Hair texture

Fine 4 (11.4%) 8 (22.9%)

Average 28 (80.0%) 24 (68.6%)

Coarse 3 (8.6%) 3 (8.6%)

Race

White 35 (100%) 35 (100%)

Values in table are presented as the average ± standarddeviation (SD) or as a number with the percentage inparenthesis

Dermatol Ther (Heidelb) (2019) 9:143–157 149

product group disagreed after the first treat-ment, whereas none of the subjects in thisgroup disagreed after the second treatment.Finally, after the first treatment, 9% of thesubjects disagreed with the statement ‘‘Greasi-ness is normal’’; however, at the end of thestudy, only 3% disagreed.

In the reference product group, 94–100% ofthe subjects responded positively to all state-ments, with the exception for that on dryness ofthe hair. Indeed, 14 and 9% of the subjects inthis group disagreed with the statement that thehair does not feel too dry after the first andsecond treatment, respectively. Furthermore,3% of the subjects strongly disagreed and 3%disagreed with the statement that the hair feelsgood after the first treatment; after the secondtreatment, none of the subjects disagreed.

With respect to the statements on shininessand volume of the hair, and the conditioningeffect, the outcomes were comparable in bothgroups for both treatments. With regards to thestatement on greasiness of the hair, 3% or noneof the subjects in the reference product group

disagreed after the first and second treatment,respectively. The results of this questionnaireare presented in detail in Table 3.

Safety Evaluation

Local TolerabilityLocal tolerability was assessed during all visits,with the following parameters being assessed:burning, paraesthesia, and pruritus. In the testproduct group, paraesthesia and burning werenot reported. Prior to treatment, pruritus wasreported by 77% of the subjects (mild 43%,moderate 23%, severe 11%). At each follow-upvisit, the number of subjects reporting pruritusgradually decreased. At study end, only 20% ofthe subjects reported mild pruritus. Moderate tosevere prurituswas not observed. In the referencegroup, paraesthesia was not reported. Only onesubject in this group complained about mildburning before the first treatment, but this didnot reoccur. Prior to treatment, pruritus wasreported by 69% of the subjects (mild 37%,

Table 2 Cure rates at different evaluation time points, after one and two treatments, respectively, together with theminimum, median, and maximum recorded number of head lice

Statistic Day 0(pre-treatment)

Day 0(post firsttreatment)

Day 1(post firsttreatment)

Day 7(pre-secondtreatment)

Day 7(post secondtreatment)

Day 10 (endof study)

Test product group (n = 35)

Minimum/median/

maximuma

5/7/92 0/0/16 0/0/13 0/0/24 0/0/2 0/0/8

Lice-free, n (%) – 29 (82.9%) 30 (85.7%) 18 (51.4%) 33 (94.3%) 30 (85.7%)

Lice-free,

n (%)—corrected

– – – – – 30/34 (88.2%)

Reference product group (n = 35)

Minimum/median/

maximuma

5/8/54 0/0/12 0/0/6 0/3/14 0/0/4 0/1/13

Lice-free, n (%) NA 20 (57.1%) 21 (60%) 4 (11.4%) 26 (74.3%) 13 (37.1%)

Lice-free,

n (%)—corrected

13/32 (40.6%)

Subjects received the first treatment on day 0 and the and second treatment on day 7a Values are the number of subjects infested with head lice

150 Dermatol Ther (Heidelb) (2019) 9:143–157

moderate 23%, severe 9%). At each follow-upvisit, the number of subjects reporting pruritusgradually decreased. At study end, 14% reportedmild pruritus (no moderate or severe cases).Moderate to severe pruritus was not observed.These results are shown inmore detail in Table 4.

Global TolerabilityAt study end, global tolerability was rated as‘‘good’’ or ‘‘very good’’. The number of subjectsin the test product group with the rating ‘‘verygood’’ was remarkably higher than that in thereference product group (65.7 vs. 48.6%,respectively).

Skin IrritationsSkin erythema was not reported in the test pro-duct group. In the reference group, one subjectreported mild erythema (24 h post treatment),but this did not reoccur at days 7 and 10,respectively. Scalp excoriation and secondaryinfections were not reported in both groups.

Eye IrritationsFor both investigational products, eye tolerabil-ity was excellent. None of the subjects sufferedfrom eye redness and irritation over all visits.

Adverse Events and Serious Adverse EventsIn both treatment groups, no (serious) adverseevents were reported.

Consumer Study Outcome

The test product scored significantly better inview of wash-out time. Briefly, an average wash-out time of 17.5 (95% CI 15.1–20.0) min and11.0 (95% CI 9.3–12.8) min was calculated forthe dimethicone reference product and the testproduct, respectively. This difference was sig-nificantly different (p\ 0.0001). The shorterwash-out time was also confirmed by theresponses to the open comments: 62% of thetest subjects indicated spontaneously that thetreatment with the dimethicone product wastime-consuming.

In case the visual aspect of the hair was notgood, consumers were allowed to performadditional washings during the days followingtreatment. Briefly, a higher number of subjectsperformed extra washings in the dimethiconereference group (41 vs. 30% with test product),with an average wash-out time of 12.5 and10.6 min for the dimethicone reference productand test product, respectively. This differencewas not significant. Combining the time forinitial washing and the extra washing time, anaverage of 22.6 min was calculated for thedimethicone reference product, whereas treat-ment time with test product was significantly(p[ 0.001) lower (14.2 min). Of note, in the testproduct group, 22% of the subjects onlyrequired one washing, whereas 71% of the

Table 3 Response to statements on esthetic questionnaire, completed after the first and second treatment, respectively

Parameter/treatment Test productgroup at T1

Test productgroup at T2

Reference productgroup at T1

Reference productgroup at T2

Hair not too dry 94 97 86 91

Scalp feels pleasant 100 100 100 97

Hair feels good 100 100 94 100

Shininess is good 97 100 97 100

Greasiness is normal 91 97 97 100

Volume is good 97 100 94 100

Conditioning effect 94 97 97 100

T1 First treatment, T2 second treatmentValues in table are presented as the percentage of subjects responding positively

Dermatol Ther (Heidelb) (2019) 9:143–157 151

Table4

Occurrenceof

adverseeventsandpruritus

during

theclinicaltrialperiod

(10days)

Adverse

events

andpruritus

Treatment

Day

0(pre-treatment)

Day

0(post

first

treatm

ent)

Day

1(post

first

treatm

ent)

Day

7(pre-secon

dtreatm

ent)

Day

7(post

second

treatm

ent)

Day

10(end

ofstud

y)

Adverse

events

Erythem

aTestproduct

33

30

00

Reference

product

00

00

00

Paresthesiaand

excoriation

Testproduct

00

00

00

Reference

product

00

00

00

Burning

Testproduct

00

00

00

Reference

product

30

00

00

Pruritus

None

Testproduct

22.9

60.0

77.1

74.3

88.6

80.0

Reference

product

31.4

62.9

85.7

77.1

91.4

85.7

Mild

Testproduct

42.9

28.6

17.1

25.7

11.4

20.0

Reference

product

37.1

31.4

14.3

20.0

8.6

14.3

Moderate

Testproduct

22.9

5.7

5.7

0.0

0.0

0.0

Reference

product

22.9

5.7

0.0

2.9

0.0

0.0

Severe

Testproduct

11.4

5.7

0.0

0.0

0.0

0.0

Reference

product

8.6

0.0

0.0

0.0

0.0

0.0

Valuesin

tablearepresentedas

thepercentage

ofsubjects

152 Dermatol Ther (Heidelb) (2019) 9:143–157

subjects positively scored the visual aspect ofthe hair after two to three washings. In contrast,significantly more washings (up to 7 or more)were required for subjects treated with thedimeticone product. Despite this higher num-ber of washings, the hair was still assessed assignificantly greasier by the subjects in thisgroup (39% of the subjects indicated that thehair was too greasy). The feel of the scalp andthe feel of the hair scored better with test pro-duct but did not significantly differ from theresults, obtained with the reference product.

DISCUSSION

In recent years, insecticide-based products forthe treatment of pediculosis capitis have beengradually replaced by alternative products witha physical mode of action, with the primarydrivers of this change being growing resistanceof head lice to the agents and safety concerns[3, 4]. Many of these newer products containsilicones (e.g., high-molecular-weight dime-thicone) and/or mineral oils. Their physicalmode of action relies on suffocation and dehy-dration of the head lice [5, 7, 8]. Although theseproducts have been proven to be safe and tohave clinical efficacy [6, 11, 19, 20], they mayhave a major disadvantage from a cosmeticpoint of view, silicones in particular. Indeed,because of their lipophilicity, these productsmay leave a residue on the hair and make it oilyand greasy [9].

Extensive research has revealed that silylatedpolyols may be interesting alternatives to

silicones. Independent in vitro experimentshave shown that the test product in this clinicaltrial, an aqueous dispersion of one of thesemolecules (Prosil), yields 100% mortality forboth lice and nits. Prosil is an interestingmolecule because it elicits its effects in anidentical manner as dimethicone. Indeed, ourmicroscopic analyses revealed that, followingtreatment, the respiratory channels of the headlice were completely filled with product in amanner comparable to dimethicone exposure.Furthermore, treated head lice appeared to behighly desiccated (see Fig. 2). Interestingly, incontrast to silicones, no build up effect on hairstrands treated in vitro with the aqueous Prosildispersion was observed.

From a chemical point of view, Prosil andother silylated polyols differ from silicones ingeneral. Indeed, the latter consists of a siloxane(Si–O–Si) bone structure, whereas the activeingredient only contains organosilicon(Si–O–C) bonds. Both types of molecules areinsoluble in polar solvents such as water. How-ever, because of their very low viscosity, sily-lated polyols can be easily dispersed andstabilized in an aqueous vehicle with mediumviscosity. This is not the case for high-molecu-lar-weight silicones, which are very viscous.One could opt for emulsification (oil in wateremulsion) to ‘‘dissolve’’ the silylated polyol intothe water phase. However, in vitro experimentaldata have shown that adulticidal activity of theagent was significantly reduced (60% mortality)after emulsification. The most plausiblehypothesis for this loss of activity after emulsi-fication is that a permanent oil-in-water

Fig. 2 Assessment of penetration of test products into the respiratory channel of the head lice

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emulsion rinses off too easily from the hair and,consequently, the product does not have suffi-cient time to affect the head lice. This possibil-ity is consistent with the notion thatpenetration of silicone or oil compounds intothe spiracles and respiratory tract is essential tokill head lice and nits. It has recently beenshown that water is not able to penetrate therespiratory system of the head lice [21], a find-ing which further supports our hypothesis.

Silylated polyalcohols have been observed toself-emulsify in polar solvents over time. Toavoid such self-emulsification, a dual chamberpackaging was developed. Briefly, the silylatedpolyol (Prosil) is dissolved in a water-free, lipo-philic vehicle, which is stored in the cap. Fol-lowing activation of the cap, this Prosil phase isreleased into the aqueous vehicle (containing aviscosity modifier, a perfume, and preserva-tives). Following shaking, the product can bedirectly applied to the hair. Interestingly, theformulation remains stable for several weekswithout any loss of in vitro activity and withoutphase separation (probably because of the rela-tively high viscosity of the product).

The present clinical trial demonstrated thattreatment with the test product resulted in ahigh cure rate of 88.2% at day 10 (corrected forre-infestation), amply exceeding the pre-definedlimit of 70%. The latter value lies closely to thehighest cure rate (67.7%) reported in a recentclinical trial with a pyrethrum-based pediculi-cide [14]. It is important to stress that, at pre-sent, this is a rather exceptional outcome. Muchlower cure rates have been observed with com-parable treatments [3, 22–27], and such lowercure rates are supported by the results obtainedwith the reference product in the present study.Indeed, over all visits, cure rates were remark-ably higher for the test product than for thecontrol at each visit, with a final cure rate of40.6% (corrected for re-infestation). Further-more, one single application of the test productwas sufficient to keep 57.1% of all patients lice-free until study end, in contrast to 2.9% in thereference product group.

The most logic explanation for the observedresults is the growing resistance of head licetowards insecticides. Indeed, over the last dec-ades, cure rates significantly reduced, with

levels dropping to 25% [28]. Knockdown resis-tance (kdr)-type mutations, resulting in nerveinsensitivity to pyrethrins and derivatives, areresponsible for this phenomenon. A recentstudy in the USA showed a high percentage oflice (up to 100%) with kdr-type mutations in allU.S. states [29]. The present study was per-formed in two centers in Florida, which wereclose to each other. For this reason, a similarresistance profile can be expected in both sites.

In general, insecticide resistance is a world-wide problem and is related to misuse andoverexposure. One recent study, performed inGermany, reported an exceptionally high curerate of 94% following two treatments with apyrethrum-based lotion. The authors stated thatthis may be related to the fact that the insecti-cide-based pediculicides require a prescriptionand, therefore, people are less exposed [11].Despite growing resistance, pyrethrin- and pyr-ethroid-based products still belong to the first-line, prescription-free treatments available inthe USA, although substance-based pediculi-cides have shown to be superior in view ofperformance and safety [6, 11, 19, 20]. As thestudy was performed in Florida, RID shampoowas used as reference in the present study.

In addition to clinical performance, theesthetic effects of the test product were evalu-ated during the trial. Subjects highly appreci-ated the cosmetic effects of the test productfollowing both applications at day 0 and day 7,respectively. Indeed, more than 90% of the testsubjects were (very) satisfied with the conditionof their hair (shininess, volume, feeling of hairand scalp, dryness, and greasiness). This wasfurther confirmed by the results of the blinded,cross-over consumer study, which showed thata significantly lower rinsing time and number ofwashings were required to restore the hair in itsoriginal form.

With respect to safety, the aqueous lotionconsists of ingredients which are approved foruse in pharmaceutical and cosmetic products.The active ingredient has a comparable chemi-cal structure to other silylated products whichare applied in a variety of cosmetic products.The clinical results showed that the product waswell-tolerated, as reflected by the absence of anyadverse events (including skin and eye

154 Dermatol Ther (Heidelb) (2019) 9:143–157

irritation). Similar observations were made forthe comparator product.

The limitations of this study include themoderated number of subjects. However, sam-ple size was calculated using the data of earlierclinical trials with silicone- or mineral oil-basedpediculicides. Power analysis confirmed thatthis scale of significant differences betweentreatments is detectable in a study population ofn = 50–100. Instead of a pyrethroid-based pro-duct, a silicone-based pediculicide might haveserved as reference, especially in view of theincreasing resistance. Also, no subgroup analy-ses were performed to evaluate the impact ofinfestation degree, hair characteristics, andother parameters. However, no remarkable dif-ferences were found in baseline parametersbetween both treatment groups. Furthermore,subgroup analyses were not foreseen in theoriginal statistical plan. Subgroup analyses mayreveal some trends but because of the relativelylow number of subjects, the power of the testswould be insufficient and, therefore, any con-clusions may not be correct, statistically seen.Finally, dry combing was used to diagnose ahead lice infestation in both treatment groups.This method may be less sensitive compared towet combing. However, the latter requires theuse of a conditioner, which in turn may have animpact on lice and thus on study outcome. Forthis reason, wet combing was not used as adiagnostic tool.

CONCLUSIONS

In conclusion, the results of the present studydemonstrated that treatment with an aqueousdispersion of a silylated polyol resulted in highcure rates compared to a pyrethrum-based,prescription-free pediculicide shampoo. Inaddition to the high safety profile of the testproduct, its esthetic effects following applica-tion were assessed to be excellent, in contrast tothe assessment of silicone-based head licetreatments, showing comparable cure rates buthaving negative effects on hair quality due towash-out difficulty and residue build-up.

ACKNOWLEDGEMENTS

Funding. Sponsorship for this study andarticle processing charges were funded by Oys-tershell Laboratories, which is also the manu-facturer of the investigational product andemployer of the co-authors Frank Eertmans andBart Rossel. The sponsor was involved in thestudy planning as well as in the decision topublish, but was not involved in data collec-tion, data analysis, and data interpretation. Allauthors had full access to all data in this studyand take complete responsibility for the integ-rity of the data and accuracy of the dataanalysis.

Medical Writing and/or Other Assis-tance. Oystershell Laboratories engaged a CROin Florida (USA), specialized in clinical trialswith pediculicides, to independently design andperform the study. Two centers were involved:Lice Source Services (Plantation) and Lice Clea-nique (Miami). Co-author Elisabeth River wasthe Principal Investigator and Lidia Serrano wasstudy monitor. We thank all subjects for par-ticipating in the clinical trial. Statistical analy-ses were performed by an independent, externalconsultant, Els Adriaens (Adriaens Consulting,Bellem, Belgium).

Authorship. All named authors meet theInternational Committee of Medical JournalEditors (ICMJE) criteria for authorship for thismanuscript, take responsibility for the integrityof the work, and have given final approval forthe version to be published.

Disclosures. Frank Eertmans is an employeeof the company Oystershell, which is thedeveloper of the test product and funder of thisstudy. Bart Rossel is an employee of the com-pany Oystershell, which is the developer of thetest product and funder of this study. ElisabethRivera is a clinical investigator, associated withthe two clinical trial centers, who performed thestudy. Lidia Serrano is a clinical investigator,associated with the two clinical trial centers,who performed the study. Els Adriaens hasnothing to disclose.

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Compliance with Ethics Guidelines. Allprocedures followed were in accordance withthe ethical standards of the responsible com-mittee on human experimentation (institu-tional and national) and with the HelsinkiDeclaration of 1964, as revised in 2013.Informed consent was obtained from allpatients for being included in the study.

Open Access. This article is distributedunder the terms of the Creative CommonsAttribution-NonCommercial 4.0 InternationalLicense (http://creativecommons.org/licenses/by-nc/4.0/), which permits any noncommer-cial use, distribution, and reproduction in anymedium, provided you give appropriate creditto the original author(s) and the source, providea link to the Creative Commons license, andindicate if changes were made.

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