PEDIATRICS Vol. 120 No. 3 September 2007, pp. 689 (doi:10.1542/peds.2007-1847)
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LETTER TO THE EDITOR |
Therapy for Head Lice: In Reply
Mark Lebwohl, MDLily Clark, MD
Jacob Levitt, MD
Department of Dermatology
Mount Sinai Medical Center
New York, NY 10029
We thank Weil for his thoughtful letter. He has expressed a number of concerns about the recommendation that malathion be considered as first-line therapy for head lice. Please allow us to allay these concerns. Although malathion and chlorpyrifos are in the same chemical class, pure malathion has a different toxicity profile than other organophosphates.1 Specifically, chlorpyrifos would seem to inhibit carboxylesterase more than malathion, resulting in greater toxicity.1 In addition, it is the "-oxon" impurities, which are potent carboxylesterase inhibitors, of both malathion and chlorpyrifos that make them harmful.1 The malathion in Ovide is pure and contains no malaoxon.
It is true that the American Academy of Pediatrics (AAP) Committee on Infectious Diseases,2 which exclusively referenced the 2002 AAP guidelines for head lice,3 recommends permethrin as first-line treatment for head lice. We cited ample evidence from literature that postdated these guidelines in support of malathion as a safe and effective first-line agent. Of note, AAP policy states that the guidelines expire after 5 years unless they are reaffirmed, revised, or retired at or before that time.
The conclusion that malathion has a greater potential for toxicity than permethrin on the basis of their respective age indications is subject to question. In the case of malathion, when the labeling of this drug was approved, studies had not yet been performed to support a lower age indication; however, no data suggest a danger in lower age groups. In fact, there are now substantial data demonstrating that malathion is safe at least down to the age of 2 years.4 Moreover, head lice is a disease of older children and adults, such that infestations under the age of 6 years are uncommon.5 Malathion has been demonstrated to be as safe as permethrin when used in the concentrations found in head lice therapies.4 Both enjoy a pregnancy category B rating.
With respect to the conflict of interest, we disclosed conflicts precisely as requested by the journal. Our conclusions were based on solid evidence and are in what we feel to be the best interest of children who are affected with head lice.
REFERENCES
- Buratti FM, Testai E. Malathion detoxification by human hepatic carboxylesterases and its inhibition by isomalathion and other pesticides. J Biochem Mol Toxicol. 2005;19 :406 –414[CrossRef][Web of Science][Medline]
- American Academy of Pediatrics. Pediculosis capitis (head lice). In: Pickering LK, ed. Red Book: 2006 Report of the Committee on Infectious Diseases. 27th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2006:488 –492
- Frankowski BL, Weiner LB; American Academy of Pediatrics, Committee on School Health the Committee on Infectious Diseases. Head lice.
Pediatrics. 2002;110
:638
–643
[Abstract/Free Full Text] - Meinking TL, Vicaria M, Eyerdam DH, Villar ME, Reyna S, Suarez G. A randomized, investigator-blinded, time-ranging study of the comparative efficacy of 0.5% malathion gel vs Ovide lotion (0.5% malathion) or Nix crème rinse (1% permethrin) used as labeled, for the treatment of head lice. Pediatr Dermatol. 2007; In press
- Burgess IF. Human lice and their management. Adv Parasitol. 1995;36 :271 –342[Medline]
PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics
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