PEDIATRICS Vol. 121 No. 1 January 2008, pp. 222-223 (doi:10.1542/peds.2007-3165)
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LETTER TO THE EDITOR |
Head Lice, Resistance, and Malathion: In Reply
Mark Lebowhl, MDLily Clark, MD
Jacob Levitt, MD
Department of Dermatology
Mount Sinai Medical Center
New York, NY 10029
We agree that malathion resistance has been widely reported outside the United States. However, the focus of our article was for therapies available in the United States. We did not intentionally omit data, nor did we seek to deceive anyone. We were careful to note in all appropriate instances that the efficacy for malathion as discussed applies to the US formulation, which, to reiterate, has 2 excipients that have been independently demonstrated to have ovicidal and/or pediculicidal properties.1,2 Furthermore, although we did not dwell on malathion resistance abroad, we did not ignore it altogether. Specifically, we noted that "British lice resistant to local malathion products were killed by the US formulation."3
With respect to "historical prohibition," that designation is incorrect. Malathion has been available in the United States for 
26 years.4 The 5-year hiatus of availability from 1994 to 1999 (we and Jackson5 were in error in stating 1998) was not related to prohibition but rather a business decision on the part of its manufacturer at the time.
Dr Ross postulates that "US head lice will follow a similar resistance pattern over time to that exhibited by head lice in the United Kingdom and Australia." Although that is certainly a possibility, Meinking et al demonstrated in 2 in vitro studies, 16 years apart, that although resistance had developed to lindane, pyrethrins, and permethrin, no resistance developed to Ovide.6–8 The fact that Ovide killed malathion-resistant lice is also reassuring.9 Ovide works today, and there has been no rigorously documented resistance to Ovide to date.
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[Abstract/Free Full Text] - Yang YC, Choi HY, Choi WS, Clark JM, Ahn YJ. Ovicidal and adulticidal activity of Eucalyptus globulus leaf oil terpenoids against Pediculus humanus capitis (Anoplura: Pediculidae). J Agric Food Chem. 2004;52 :2507 –2511[CrossRef][Web of Science][Medline]
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[Abstract/Free Full Text] - US Food and Drug Administration, Center for Drug Evaluation and Research. Approval letter [Ovide]. Available at: www.fda.gov/cder/foi/nda/99/18613s009s010_ovide.pdf. Accessed October 19, 2007
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[Abstract/Free Full Text] - Meinking TL, Entzel P, Villar ME, Vicaria M, Lemard GA, Porcelain SL. Comparative efficacy of treatments for Pediculosis capitis infestations: update 2000.
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[Abstract/Free Full Text] - Meinking TL, Serrano L, Hard B, et al. Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States.
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[Abstract/Free Full Text] - Downs AM, Narayan S, Stafford KA, Coles GC. Effectiveness of Ovide against malathion-resistant head lice.
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PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics
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