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.