A new ivermectin formulation topically kills permethrin-resistant human head lice (Anoplura: Pediculidae)

J Med Entomol. 2008 Jan;45(1):75-81. doi: 10.1603/0022-2585(2008)45[75:aniftk]2.0.co;2.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Dose-Response Relationship, Drug
  • Insecticide Resistance*
  • Insecticides / pharmacology*
  • Ivermectin / pharmacology*
  • Permethrin / pharmacology*
  • Phthiraptera / drug effects*
  • Time Factors

Substances

  • Insecticides
  • Permethrin
  • Ivermectin