From the Guidelines
Pediculosis capitis treatment with permethrin 5% is not recommended as the standard treatment, instead, permethrin 1% is the preferred option. The most recent and highest quality study available is from 2010, published in the journal Pediatrics 1. According to this study, permethrin 1% has been the most studied pediculicide in the United States and is the least toxic to humans.
Key Points to Consider
- Permethrin 1% is currently recommended as one of the drugs of choice for head lice, and it is applied to damp hair that is first shampooed with a nonconditioning shampoo and then towel dried.
- The product is left on for 10 minutes and then rinsed off, and it leaves a residue on the hair that is designed to kill nymphs emerging from the 20% to 30% of eggs not killed with the first application.
- However, conditioners and silicone-based additives present in almost all currently available shampoos impair permethrin adherence to the hair shaft and reduce its residual effect, therefore, it is suggested that the application be repeated in 7 to 10 days if live lice are seen.
- Many experts now recommend routine re-treatment, preferably on day 9, and an alternate treatment schedule on days 0,7, and 13 to 15 has been proposed for nonovidal products.
Important Considerations
- Resistance to 1% permethrin has been reported, but the prevalence of this resistance is not known.
- Permethrin is a synthetic pyrethroid with extremely low mammalian toxicity, and reported adverse effects include pruritus, erythema, and edema.
- Permethrin is less allergenic than pyrethrins and does not cause allergic reactions in individuals with plant allergies.
Treatment Approach
- Apply permethrin 1% to clean, damp hair, ensuring complete coverage from scalp to hair ends.
- Leave it on for 10 minutes, then rinse thoroughly with water.
- A single application is often sufficient, but a second treatment 7-10 days later is recommended to kill any newly hatched lice from eggs that survived the first application.
- For best results, use a fine-toothed comb to remove dead lice and nits after treatment.
From the Research
Treatment of Pediculosis Capitis with Permethrin 5%
- Permethrin 5% is a common treatment for pediculosis capitis, however, the provided studies compare the efficacy of permethrin 1% with spinosad 0.9% 2, 3.
- According to the studies, spinosad 0.9% was significantly more effective than permethrin 1% in the eradication of head lice, with most spinosad-treated participants requiring only a single treatment 2, 3.
- Permethrin 1% was found to have a lower efficacy rate, with 44.9% and 42.9% of participants being lice-free after treatment, compared to 84.6% and 86.7% for spinosad 0.9% 2.
- The use of permethrin 5% is not specifically mentioned in the provided studies, but permethrin is listed as a treatment option for pediculosis capitis in general 4, 5, 6.
- It is worth noting that the development of resistance to permethrin has been reported, and alternative treatments such as spinosad, ivermectin, and benzyl alcohol are being considered 5, 6.