Efficacy of a Reduced Application Time of Ovide Lotion (0.5% Malathion) Compared to Nix Creme Rinse (1% Permethrin) for the Treatment of Head Lice

Abstract

Our objective was to conduct a randomized, investigator-blinded evaluation of the pediculicidal and ovicidal activity of a reduced application time (20 minutes) of Ovide (0.5% malathion) compared to Nix (1% permethrin) in a south Florida population infested with Pediculus humanus capitis. Either Ovide or Nix was applied according to the label instructions. However, Ovide application time was reduced to 20 minutes. At day 8, subjects with live lice were re-treated with the same product and procedure as on day 1. Ovicidal and pediculicidal efficacy were evaluated at days 8 and 15. A subject free of lice and viable eggs at day 15 was considered to be a treatment success. Percent efficacy was calculated using the number of subjects free of lice and viable eggs per total number of subjects treated. We found that a 20-minute application of Ovide was significantly more pediculicidal and ovicidal (98%) compared to Nix (55%) at day 15 (p < 0.0001). The percentage of Ovide subjects who required treatment at day 8 was half that of the Nix group. The reinfestation rate was 0% with Ovide and 33% with Nix. In conclusion, a 20-minute treatment with Ovide, instead of the approved 8- to 12-hour application, cured 40 of 41 subjects (98%), demonstrating superior efficacy to Nix. The poor efficacy of Nix confirms the resistance of head lice to permethrin in south Florida.

Head Lice

“…It is available only by prescription as a lotion that is applied to dry hair, left to air dry, then washed off after 8 to 12 hours, although some study results have suggested effectiveness when left on for as short a time as 20 minutes. 37 Head lice in the United Kingdom and elsewhere have shown resistance to malathion preparations, which have been available for decades in those countries. 38,39 The current US formulation of malathion (Ovide lotion, 0.5%) differs from the malathion products available in Europe in that it contains terpineol, dipentene, and pine needle oil, which themselves have pediculicidal properties 25 and may delay development of resistance.…”

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

“…In Israel (Mumcuoglu et al 1991), the efficacy of 14 products had been tested according to the manufacturer's instructions but with in vitro tests with raring body lice (Pediculus humanus humanus). Other similar ex vivo efficacy tests of pediculicides available on their market are as follows: one in Egypt (Abdel-Ghaffar et al 2010) on 13 anti-head-lice products, not according to the manufacturer's instructions and without testing ovicidal efficacy, another in the USA (Meinking et al 1986), testing the pediculicidal activity of six pediculicides but not according to the manufacturer's instructions.…”

“…The assay was performed in respect of the manufacturer recommendations on a laboratory colony of body lice (P. humanus humanus) and their eggs. In other similar studies, the contact time in the assay differed from the contact time recommended by the manufacturer (Meinking et al 1986;Meinking et al 2001;Heukelbach et al 2008aHeukelbach et al , 2009Abdel-Ghaffar 2010;Gallardo et al 2012).…”

“…Relying on products alone to contain head louse infestations at a reasonable level will not be sufficient. Public health programs at local community level involving parents, schools, and community services with accurate screening methods (Combescot 1990;Demaeseneer et al 2000;Mumcuoglu et al 2007;Jahnke 2009) and synchronized treatment campaigns with effective treatments will be needed (Meinking et al 1986;Combescot 1990;Ibarra et al 2007;Feldmeier 2012).…”

Head Lice Treatments and School Policies in the US in an Era of Emerging Resistance

“…[10] Yet, concerns about emerging head lice resistance to permethrin worldwide have been raised. [11][12][13][14][15][16][17][18] It is also clear that as permethrin resistance increases, its effectiveness for lice treatment is correspondingly reduced. Moreover, the information regarding the specific susceptibility or resistance of head lice in a particular geographical area is not readily available for both the public and health providers.…”