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

Abstract

BackgroundDimeticones 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.MethodsWe 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.ResultsAfter 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.ConclusionsThe 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.

Ovicidal Response of NYDA Formulations on the Human Head Louse (Anoplura: Pediculidae) Using a Hair Tuft Bioassay

“…Of these types of products, dimeticone-based antilouse products (silicone oils) have attracted a good amount of attention because of their low mammalian toxicity, novel modes of action that are not neurotoxic and the possibility that they will have a low potential for the development of resistance (Heukelbach et al 2009). …”

Ex vivo effectiveness of French over-the-counter products against head lice (Pediculus humanus capitis De Geer, 1778)

“…Regarding Duo LP Pro®, a controlled clinical study (Militao de Sousa et al 2009) and an ex vivo experiment with Liberalice® (Duo LP Pro®) (Heukenbach et al 2009) were conducted. However, in the latter study, the authors observed that Liberalice® was less effective, but they did not expose the lice for 8 h as it is asked in the manufacturer's instructions.…”

Medizinprodukte in der Dermatologie: Topische halbfeste Formulierungen zur Behandlung von Hauterkrankungen

“…Bereits nach fünf Minuten und an allen weiteren Untersuchungszeitpunkten zeigten alle Läuse keine wesentlichen Lebenszeichen mehr, was von keiner der Vergleichssubstanzen bzw. -zubereitungen (0,5 % Permethrin, 4 % Dimeticon, Soja-Kokosnussöl, 0,3 % Pyrethrumextrakt) erreicht wurde [31,32]. Auch in der abtötenden Wirkung war das Medizinprodukt den Vergleichssubstanzen überlegen: Nach einer Inkubationszeit von nur einer Stunde betrug die Schlupfrate bei jungen Eiern 0 % und bei reifen Eiern 3,9 %, während die Schlupfraten bei den Vergleichssubstanzen mindestens bei 35 % lagen [33].…”