High in vitro efficacy of Nyda L, a pediculicide containing dimeticone

Effectiveness and tolerability of a squalane and dimethicone-based treatment for head lice

Head lice (Pediculus humanus capitis) are worldwide obligate human ectoparasites, with high implications in pediatrics. In Europe, first-line topical neurotoxic insecticidal therapeutic strategies are being replaced by topical physically acting agents as the first-choice treatment. Safety of the active ingredients and high efficacy in a one-time single-dose treatment with a brief treatment application time are key issues for consumer use and effective compliance. The aim of this study was to assess the in vitro efficacy of a newly developed squalane and dimethicone-based pediculicidal formula, against motile head lice and eggs after 2 and 5 min immersion in the product, as well as its skin tolerance and acceptability under dermatological and pediatric expert control in children with atopic skin. The results indicate that at both time points, 100% mortality rate of head lice crawling stages and late-stage eggs was achieved. The formula was well tolerated and suitable for children with atopic skin from 12 months of age. Showing high in vitro efficacy and good skin acceptability, this solution is presented as a new safe alternative therapy for treatment of head lice infestations.

High efficacy of a dimeticone-based pediculicide following a brief application: in vitro assays and randomized controlled investigator-blinded clinical trial

Background

Increasing resistance of head lice against neurotoxic agents and safety concerns have led to the search for treatment alternatives. Dimeticones with a physical mode of action are safe, and bear a reduced risk for the development of resistance.

Methods

We performed in vitro bioassays to assess pediculicidal and ovicidal activities of a new dimeticone-based product, and a randomized controlled clinical trial to assess efficacy, following 10 min application. Of 153 individuals screened, 100 participants with active head louse infestations were randomly assigned to treatment with either a dimeticone-based test product, or a 0.5% permethrin-based reference product (50 participants per group). Participants received two topical applications of either the test (10 min) or reference products (45 min) at days 0 and 7 or 8. Outcome measures included the efficacies of treatment and their safety, as well as global and local tolerability at baseline, and days 1, 7, and 10.

Results

After 10 min exposure, all lice treated with the dimeticone test product were classified as non-viable in the in vitro assay. Ovicidal activity after treatment of eggs with the dimeticone test product was 96.8%. In the clinical trial, 96 patients completed all study visits. In the full analysis set (FAS) population, on day 1 after one application, 98% of patients were cured in the test group, as compared to 84% cured in the reference group. All participants in both groups were free of head lice on day 10, following two applications (100% cure rate). In total, 42 adverse events (AEs) in 23 patients of both treatment groups were recorded, with the majority of AEs classified as mild.

Conclusions

We have shown a high level of pediculicidal and ovicidal activity, and clinical efficacy and safety, of a brief application of a new dimeticone-based product. The short application time and reduced risk for the development of resistance are key drivers for improved patients’ compliance.

Trial registration

EU Clinical Trials Register EudraCT 2016–004635-20. Registered 14 November 2016.

Do drowning and anoxia kill head lice?

Chemical, physical, and mechanical methods are used to control human lice. Attempts have been made to eradicate head lice Pediculus humanus capitis by hot air, soaking in various fluids or asphyxiation using occlusive treatments. In this study, we assessed the maximum time that head lice can survive anoxia (oxygen deprivation) and their ability to survive prolonged water immersion. We also observed the ingress of fluids across louse tracheae and spiracle characteristics contrasting with those described in the literature. We showed that 100% of lice can withstand 8 h of anoxia and 12.2% survived 14 h of anoxia; survival was 48.9% in the untreated control group at 14 h. However, all lice had died following 16 h of anoxia. In contrast, the survival rate of water-immersed lice was significantly higher when compared with non-immersed lice after 6 h (100% vs. 76.6%, p = 0.0037), and 24 h (50.9% vs. 15.9%, p = 0.0003). Although water-immersed lice did not close their spiracles, water did not penetrate into the respiratory system. In contrast, immersion in colored dimeticone/cyclomethicone or colored ethanol resulted in penetration through the spiracles and spreading to the entire respiratory system within 30 min, leading to death in 100% of the lice.

Safety, Efficacy, and Physicochemical Characterization of Tinospora crispa Ointment: A Community-Based Formulation against Pediculus humanus capitis

The high prevalence of pediculosis capitis, commonly known as head lice (Pediculus humanus capitis) infestation, has led to the preparation of a community-based pediculicidal ointment, which is made of common household items and the extract of Tinospora crispa stem. The present study aimed to evaluate the safety, efficacy, and physicochemical characteristics of the T. crispa pediculicidal ointment. The physicochemical properties of the ointment were characterized, and safety was determined using acute dermal irritation test (OECD 404), while the efficacy was assessed using an in vitro pediculicidal assay. Furthermore, the chemical compounds present in T. crispa were identified using liquid-liquid extraction followed by ultra-performance liquid chromatography quadruple time-of-flight mass spectrometric (UPLC-qTOF/MS) analysis. The community-based ointment formulation was light yellow in color, homogeneous, smooth, with distinct aromatic odor and pH of 6.92±0.09. It has spreadability value of 15.04±0.98 g·cm/sec and has thixotropic behavior. It was also found to be non-irritant, with a primary irritation index value of 0.15. Moreover, it was comparable to the pediculicidal activity of the positive control Kwell^®, a commercially available 1% permethrin shampoo (P>0.05), and was significantly different to the activity of the negative control ointment, a mixture of palm oil and candle wax (P<0.05). These findings suggested that the community-based T. crispa pediculicidal ointment is safe and effective, having acceptable physicochemical characteristics. Its activity can be attributed to the presence of compounds moupinamide and physalin I.

Assessment of the efficacy and safety of a new treatment for head lice

Infestation with head lice is a widespread, persistent, and recurring issue leading to serious health problems if untreated. We are facing resistance phenomena to usual pediculicides and questions about their direct or cumulative toxicity. The aim of this trial was to assess the efficacy of a new product, free of chemical insecticides but with a physical effect. This product contains components whose antilice efficacy has already been demonstrated, as well as Andiroba oil which asphyxiates the lice and Quassia vinegar which dissolves the chitin of the nits (they are then inactivated). 30 patients with head lice infestation, aged 3–39 years, applied the treatment one to three times, 5 days apart. Cure was defined as the absence of live lice after 5, 10, or 14 days, and symptoms are usually associated with infestation. Easiness and safety of the treatment were assessed by the patients and/or their parents. Overall cure rates were 20% on D5 after one treatment, 37% on D10 after two treatments, and 90% on D14 after three treatments. Symptoms such as itch, scalp dryness, redness, and flakiness rapidly diminished. This treatment seems to be a beneficial addition or a valuable alternative to existing treatments, considering the total absence of chemical insecticides, the absence of drug-resistance induction in head lice, the absence of major toxicological risks compared with usual pediculicides, and the favourable patient use instructions.

Safety and efficacy of a non-pesticide-based head lice treatment: results of a randomised comparative trial in children

BACKGROUND/OBJECTIVES

Increasing resistance to pesticide-based head lice treatments has resulted in the need for alternative products to treat head lice infestations, but there are few clinical studies that have adequately tested these products. This multicentre, randomised, assessor-blind, parallel-group phase IV trial compared the safety and efficacy of a non-pesticide-based head lice shampoo with malathion foam in children.

METHODS

This trial used strict entry criteria, standardised treatment and assessment regimes, sibling control and a primary efficacy end-point defined as the absence of live head lice 21 days after initiating treatment. Repeat insult patch tests were performed to further assess the safety of the non-pesticide-based shampoo. In vitro tests were used to assess its ovicidal and pediculicidal efficacy.

RESULTS

A total of 216 children were enrolled, of whom 172 were per-protocol. The non-pesticide-based shampoo was significantly more effective than malathion foam for the intent-to-treat population (62.3 vs 40.4% louse-free, unadjusted P = 0.002; adjusted P = 0.003), as well as for the per-protocol population (67.8 vs 43.0% louse-free, unadjusted P = 0.001; adjusted P = 0.004). Adverse events were limited to itching or stinging. Patch testing with the non-pesticide-based shampoo resulted in no adverse reactions. In vitro tests using body lice demonstrated that the non-pesticide-based shampoo is ovicidal and pediculicidal.

CONCLUSION

The non-pesticide-based shampoo is significantly more effective in eliminating head lice than malathion foam in children, while being associated with a low incidence of mild, transient adverse events.

Medical devices in dermatology: topical semi-solid formulations for the treatment of skin diseases

In recent years, topically applied semi-solid formulations certified as medicals devices and not as topical drugs are increasingly used for the treatment of skin diseases. Medical devices primarily unfold their therapeutic effect by physical means, not by pharmacological, immunological or metabolic means. Intensified placing of medical devices on the dermatological market may at least partly be explained by a less complex marketing authorization process compared to topical drugs. If the requirements are fulfilled to certify a product as a medical device the opportunity will be offered to quickly introduce innovations onto the market and propagate them. A variety of evidence-based medical devices for several dermatological indications are presented here.

A randomized, assessor-blind, parallel-group, multicentre, phase IV comparative trial of a suffocant compared with malathion in the treatment of head lice in children

BACKGROUND/OBJECTIVES

There are concerns about the effectiveness of head lice treatments because of increasing resistance and safety. This trial compared the safety and efficacy of a suffocant-based head lice treatment to malathion in children.

METHODS

The trial used strict entry criteria, standardized treatment and assessment regimens, sibling treatment where appropriate and a primary efficacy end-point defined as the absence of live head lice.

RESULTS

A total of 216 children were enrolled. One hundred and sixty-nine were per-protocol. The suffocant was significantly more effective than malathion for the intention-to-treat population (53.9% vs 40.4% louse-free, unadjusted P = 0.052; adjusted P = 0.024), as well as for the per-protocol population (57.8% vs 43.0% louse-free, unadjusted P = 0.054; adjusted P = 0.045). Adverse events were limited to itching or stinging and there were no serious or systemic adverse events. Repeat insult patch testing with the suffocant resulted in no adverse reactions. In vitro tests confirmed that the suffocant is a potent ovicide and pediculicide with 100% mortality of eggs and lice following a 20-min contact time.

CONCLUSIONS

The suffocant is shown to be significantly more effective in eliminating head lice than malathion in children, while being associated with a low incidence of mild, transient adverse events.

Efficacy of chemical and botanical over-the-counter pediculicides available in Brazil, and off-label treatments, against head lice ex vivo

BACKGROUND

There is a lack of reliable data on the efficacy of over-the-counter (OTC) pediculicides in Brazil.

METHODS

We performed ex vivo assays of eight marketed pediculicides: 1% permethrin (Kwell, Clean Hair, Keltrina, Nedax), 0.02% deltamethrin (Deltacid, Pediderm), and two "natural" products (Piolho e Lêndea, Pilogenio). We also tested 5% permethrin (Keltrina Plus), traditional home remedies and an ivermectin-based product used in veterinary medicine. Head lice (49-52 per group) were immersed in the compound for 3 min and washed after 20 min to simulate the typical in vivo treatment protocol. Lice were examined for activity up to 24 h using stringent criteria for survival.

RESULTS

Of the permethrin containing products, highest mortality was observed with Kwell and Clean Hair (97.9 and 90.2% after 4 h). Keltrina, Nedax, Keltrina Plus, and the two deltamethrin-based products showed only a low efficacy of <60% after 4 h. With exception of pure coconut oil (80% mortality after 4 h), home remedies showed a very low efficacy, and both marketed products killed few lice. The ivermectin-based product caused a mortality of 100% after 4 h.

CONCLUSIONS

Most Brazilian OTC products did not show a satisfactory efficacy against head lice. Resistance may be present. Ivermectin and coconut oil are promising compounds for topical treatment. Laboratory-based tests should be used to assess resistance patterns and to identify formulations of the active ingredient that increase the efficacy. Standardized testing should be performed before a product is licensed for head lice treatment.

Clinical trial showing superiority of a coconut and anise spray over permethrin 0.43% lotion for head louse infestation, ISRCTN96469780

Permethrin is the most widely used pediculicide, but evidence of resistance from several countries and anecdotal reports from Germany suggest that permethrin lotion is now less effective. We designed a randomized, controlled, parallel group trial involving 100 participants with active head louse infestation to investigate the activity of a coconut and anise spray and to see whether permethrin lotion is still effective, using two applications of product 9 days apart. The spray was significantly more successful (41/50, 82.0%) cures compared with permethrin (21/50, 42.0%; p < 0.0001, difference 40.0%, 95% confidence interval of 22.5% to 57.5%). Per-protocol success was 83.3% and 44.7%, respectively. Thirty-three people reported irritant reactions following alcohol contact with excoriated skin. We concluded that, although permethrin lotion is still effective for some people, the coconut and anise spray can be a significantly more effective alternative treatment.

A new two-phase dimeticone pediculicide shows high efficacy in a comparative bioassay

BACKGROUND

Dimeticones kill head lice by physical means. Here we assessed in a comparative bioassay the ex vivo efficacy of "NYDA sensitiv", a new two-phase dimeticone-based pediculicide similar to a product established on the market, but without fragrances.

METHODS

We compared efficacy of the new product to a positive dimeticone control group, a sample of four other insecticidal and natural head lice products marketed in Germany, and an untreated control. In a bioassay, lice were exposed ex vivo to products and examined for activity for up to 24 hours, following a standard protocol.

RESULTS

After 6 and 24 hours, 13.7 and 88.5% of untreated control lice did not show major vital signs. In contrast, no lice showed major vital signs 5 minutes after treatment with the new product or the control dimeticone group (NYDA). This effect persisted at all observation points (100% efficacy). Efficacy of 0.5% permethrin (Infectopedicul) ranged between 76 and 96% in evaluations between 5 min and 6 hours. All lice treated with a coconut-based compound (mosquito Läuseshampoo) did not show major vital signs after 5 min, but mortality was only 58% after one hour. Pyrethrum extract (Goldgeist forte) showed an efficacy of 22 - 52% between 5 min and 3 hours after treatment; after 6 hours, 76% of lice were judged dead. An oxyphthirine-based compound (Liberalice DUO LP-PRO) killed 22 - 54% of lice in the first 6 hours.

CONCLUSIONS

The two-phase dimeticone compound NYDA sensitiv is highly efficacious. The removal of fragrances as compared to an established dimeticone product did not affect in vitro efficacy.

Comparative in vitro tests on the efficacy and safety of 13 anti-head-lice products

Head lice are an emerging social problem, not only in economically poor countries but also in practically all other societies. Several of the common anti-louse products have lost--at least in part--their efficacy due to increasing resistance of lice against insecticides such as permethrin or allethrin. Other compounds, like lindan, were redrawn or banned due to high toxicity. Some recently developed products are based on dimethicones or cyclomethicones and turned out to be easily inflammable. Other styled medicinal products are based on plant extracts-some were proven of high efficacy-others of ineffectivity. The present study investigated in in vitro tests the anti-head louse efficacy of 13 products, the contents of which are used worldwide: Aesculo-Gel L, EtoPril, Goldgeist Forte, InfectoPedicul, Jacutin Pedicul Fluid, K.Laus, Liberalice, Licatack, Mosquito Läuse-Shampoo, Nyda, Paranix, Picksan Louse Stop, and Wash Away Louse. It turned out that several of them are easily inflammable, and therefore, they endanger users (InfectoPedicul, Paranix, EtoPril, Nyda, Goldgeist Forte, and K.Laus, see Table 1). Others have to remain for many hours on the hair in order to reach efficacy (Table 4). During such long periods, highly dosed oils may become inhaled and thus may become dangerous for the user's lung epithelia by covering them. When incubating the lice for 3 or 10 min in vitro, only the following products killed all lice exposed to these products: InfectoPedicul, Paranix, Jacutin Pedicul Fluid, Nyda, K.Laus, Picksan Louse Stop, Licatack, and Wash Away Louse. When evaluating the possible dangers for the users, the last three products, especially, derived from plant extracts, are safe and highly effective at the same time. Furthermore, they had been tested dermatologically as "very good".

The mode of action of dimeticone 4% lotion against head lice, Pediculus capitis

Background

Treatment of head lice using physically acting preparations based on silicones is currently replacing insecticide use due to widespread resistance to neurotoxic agents. It has been postulated that some products act by asphyxiation, although the limited experimental evidence and the anatomy of the louse respiratory system suggest this is unlikely.

Results

Observation over several hours of lice treated using 4% high molecular weight dimeticone in a volatile silicone base showed that, although rapidly immobilised initially, the insects still exhibited small movements of extremities and death was delayed. One common effect of treatment is inhibition of the louse's ability to excrete water by transpiration through the spiracles. Inability to excrete water that is ingested as part of the louse blood meal appears to subject the louse gut to osmotic stress resulting in rupture. Scanning electron microscopy coupled with X-ray microanalysis to detect silicon showed dimeticone lotion is deposited in the spiracles and distal region of the tracheae of lice and in some cases blocks the lumen or opening entirely.

Conclusion

This work raises doubts that lice treated using dimeticone preparations die from anoxia despite blockage of the outer respiratory tract because movements can be observed for hours after exposure. However, the blockage inhibits water excretion, which causes physiological stress that leads to death either through prolonged immobilisation or, in some cases, disruption of internal organs such as the gut.

A highly efficacious pediculicide based on dimeticone: randomized observer blinded comparative trial

Background

Infestation with the human head louse (Pediculus humanus capitis) occurs worldwide. Existing treatment options are limited, and reports of resistance to commonly used pediculicides have been increasing. In this trial we assessed the efficacy of a product containing a high (92%) concentration of the silicone oil dimeticone (identical in composition to NYDA^®), as compared to a 1% permethrin lotion.

Methods

Randomized, controlled, observer blinded clinical trial. Participants were recruited from a poor urban neighbourhood in Brazil where pediculosis capitis was highly prevalent. To minimize reinfestation during the trial, participants (145 children aged 5–15 years with head lice infestations) were transferred to a holiday resort outside the endemic area for a period of 9 days. Two applications of dimeticone or 1% permethrin were done, seven days apart. Outcome measures were defined as cure (absence of vital head lice) after first application and before and after second applications, degree of itching, cosmetic acceptability, and clinical pathology.

Results

Overall cure rates were: day 2 – dimeticone 94.5% (95% CI: 86.6% – 98.5%) and permethrin 66.7% (95% CI: 54.6% – 77.3%; p < 0.0001); day 7 – dimeticone 64.4% (95% CI: 53.3% – 75.3%) and permethrin 59.7% (95% CI: 47.5% – 71.1%; p = 0.5); day 9 – dimeticone 97.2% (95% CI: 90.3% – 99.7%) and permethrin 67.6% (95% CI: 55.4%-78.2%); p < 0.0001). Itching was reduced similarly in both groups. Cosmetic acceptability was significantly better in the dimeticone group as compared to the permethrin group (p = 0.01). Two mild product-related incidents occurred in the dimeticone group.

Conclusion

The dimeticone product is a safe and highly efficacious pediculicide. Due to its physical mode of action (interruption of the lice's oxygen supply of the central nervous system), development of resistance is unlikely.

Trial registration

Current Controlled Trials ISRCTN15117709.

In vitro efficacy of over-the-counter botanical pediculicides against the head louse Pediculus humanus var capitis based on a stringent standard for mortality assessment

Infestation of the head louse Pediculus humanus var capitis DeGeer (Phthiraptera: Pediculidae) is an important public health problem in Australia, with up to a third of children infested in some primary schools. Insecticide resistance and inadequate attention to the application instructions of topical pediculicides are common reasons for treatment failure. This study evaluated six popular Australian over-the-counter products against head lice, primarily comprised of different botanical extracts, and compared them with permethrin 1% (Quellada) and a non-treatment control in order to assess their in vitro efficacy. We also assessed commonly used criteria for evaluating pediculicide efficacy in vitro. All tested products failed to demonstrate high levels of efficacy with the exception of Tea Tree Gel((R)), which outperformed 1% permethrin. Permethrin had a high level of efficacy, but using stringent criteria 18% of lice were not dead at 3 h, indicating some resistance to Quellada. Commonly used less stringent criteria were shown to overestimate mortality of head lice as a result of the protective phenomenon of stasis or sham death observed in exposed lice that may recover after some time. Using two different levels of stringency resulted in different rankings of efficacy for most products, with the exception of the first ranked product, Tea Tree Gel. Rankings of efficacy also varied over time, even within the different assessment criteria. Government regulatory agencies should require standard in vitro tests using stringent mortality criteria, with an observation period of >or= 6 h, to determine the efficacy of new pediculicides, and only products that cause a minimum mortality rate (e.g. 80%) in head lice collected from the target population should be licensed for sale.