title: A new ivermectin formulation topically kills permethrin-resistant human head lice (Anoplura: Pediculidae).
abstract: This study examines the effectiveness of a new ivermectin formulation for the topical treatment of the human head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae). Permethrin-resistant lice originally obtained from south Florida and maintained on an in vitro rearing system were 100% susceptible to ivermectin formulations by using a semiclinical hair tuft bioassay. The formulation was 100% effective at killing lice using 1, 0.5, and 0.25% ivermectin concentrations after 10-min exposures. As judged by the lethal time (LT)50 and LT95 values, 0.5% formulated ivermectin was 3.8 and 3.2 times faster at killing lice, respectively, than 0.5% nonformulated ivermectin, indicating that the formulation may facilitate the penetration of ivermectin into the louse. The hair tuft-based bioassay in conjunction with the in vitro rearing system provides a standardized method to assess the comparative efficacy of pediculicide formulations in a reproducible format that mimics the exposure scenario that occurs on the human scalp.
authors.affiliation: Department of Veterinary and Animal Science, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Strycharz
authors.forename: Kyong Sup
authors.initials: KS
authors.lastname: Yoon
authors.forename: J Marshall
authors.initials: JM
authors.lastname: Clark
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D007559:Ivermectin / Q000494:pharmacology*; D026023:Permethrin / Q000494:pharmacology*; D008003:Phthiraptera / Q000187:drug effects*; D013997:Time Factors
chemical_list: D007306:Insecticides; D026023:Permethrin; D007559:Ivermectin