Controlled study of malathion and d-phenothrin lotions for Pediculus humanus var capitis-infested schoolchildren

Lancet. 1994 Dec;344(8939-8940):1724-7. doi: 10.1016/s0140-6736(94)92884-3.


Anecdotal reports have suggested that reduced efficacy of pediculicides against Pediculus humanus capitis could be related to resistance to treatments. Ovicidal and pediculicidal activities of 0.5% malathion and 0.3% d-phenothrin lotions were tested in an experimental model of P humanus capitis grown on rabbits to ensure that the two treatments were pharmacologically equipotent. We then did a randomised controlled trial in which the lotions were administered to 193 P humanus capitis-infested schoolchildren (malathion, 95; d-phenothrin, 98). Success rate was defined as the absence of both live lice and viable nits. Before treatment, live lice were collected and subjected to a pediculicidal test. Pharmacological tests showed 100% killing of the rabbit-grown nits and lice after exposure to both pediculicides. On day 1 of the controlled trial, the success rate was 92% in the malathion group (95% CI, 0.86-0.97) and 40% in the d-phenothrin group (0.30-0.49) (p < 0.0001); on day 7, it was 95% in the malathion group (0.90-0.99) and 39% in the d-phenothrin group (0.29-0.48, p < 0.0001). Malathion was also significantly more active in the pediculicidal tests compared to d-phenothrin and control. These results suggest an acquired resistance to d-phenothrin in the schoolchildren tested, since all other conditions of the administration of insecticides were standardised.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Child
  • Female
  • Humans
  • Insecticide Resistance
  • Lice Infestations / drug therapy*
  • Malathion / administration & dosage*
  • Malathion / pharmacology
  • Malathion / therapeutic use
  • Male
  • Pediculus / drug effects
  • Pyrethrins / administration & dosage*
  • Pyrethrins / pharmacology
  • Pyrethrins / therapeutic use
  • Rabbits
  • Scalp Dermatoses / drug therapy*


  • Pyrethrins
  • phenothrin
  • Malathion