What is the role of pediculicides in the treatment of pediculosis and pthiriasis (lice infestation)?

Updated: Aug 16, 2019
  • Author: Lyn C C Guenther, MD, FRCPC, FAAD; Chief Editor: Michael Stuart Bronze, MD  more...
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Not all treatment preparations are ovicidal. For weakly ovicidal or non-ovicidal pediculicides, routine retreatment is recommended typically 7-9 days after the first treatment. For strongly ovicidal pediculicides, retreatment is recommended only if live (ie, crawling) lice are still present after treatment. [4] Retreatment should ideally occur after all eggs have hatched but before new eggs are produced. [4] It is extremely important to use medications as directed to ensure total eradication of the lice through their life cycle. Different head lice medications should not be used at the same time. In addition, all infested persons in a household and their infested close contacts and bedmates should be treated at the same time. If an approved treatment has been properly applied and live lice are still present, a full course of treatment of another class of topical medication should be used. [32] The Canadian Pediatric Society recommends pyrethrins and permethrin as first-line treatments and isopropyl myristate and dimethicone as second-line therapies in cases of treatment failure. [32]

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