What is the use of permethrin (topical insecticide) ointment?

From the Guidelines

Permethrin ointment is a first-line treatment for scabies and lice infestations, with a recommended application of 5% permethrin cream from neck to toes for 8-14 hours before washing off, as stated in the 2015 guidelines for sexually transmitted diseases treatment 1. The treatment regimen for scabies involves applying permethrin 5% cream to all areas of the body from the neck down and washing it off after 8–14 hours, with infants and young children being treated with permethrin 1. For head lice, 1% permethrin lotion is applied to clean, damp hair for 10 minutes before rinsing, as recommended in the 2010 Pediatrics journal article on head lice 1. Some key points to consider when using permethrin ointment include:

• Common side effects, such as temporary skin irritation, burning, or stinging
• The importance of treating all household members and close contacts simultaneously to prevent reinfestation
• Washing bedding and clothing in hot water to prevent reinfestation
• The need for pregnant women to consult healthcare providers before using permethrin
• The safety of permethrin for adults and children over 2 months old, with minimal absorption into human skin 1. The most effective treatment approach involves a second application of permethrin 7-10 days after the initial treatment to kill newly hatched mites, as well as routine re-treatment on day 9 if live lice are seen 1.

From the FDA Drug Label

Permethrin Cream, 5% is indicated for the treatment of infestation with Sarcoptes scabiei (scabies). Permethrin Cream, 5% is a topical scabicidal agent for the treatment of infestation with Sarcoptes scabiei (scabies). The use of permethrin (topical insecticide) ointment is for the treatment of scabies, caused by the mite Sarcoptes scabiei.

• Main use: Treatment of scabies infestation
• Key action: Topical scabicidal agent 2 2

From the Research

Use of Permethrin Ointment

• Permethrin is a topical insecticide used to treat scabies and pediculosis, with low mammalian toxicity and virtually no allergic side-effects 3
• A 5% permethrin cream is effective in treating scabies, with a single "head to toe" application ideal for eradication programs 3
• Permethrin is recommended in scabies therapy for premature infants, small children, patients with seizures and neurological complications, and pregnant women and nursing mothers 3
• A study found that 5% permethrin cream, applied once daily for two consecutive days, is more effective than a single application in adult immunocompetent patients with scabies 4
• Another study suggested that scalp-to-toes application of permethrin may be necessary in some cases, particularly in infants and older adults with scalp involvement 5
• However, a recent study found that topical permethrin 5% had a lower cure rate compared to benzyl benzoate 25% in the treatment of scabies, with a cure rate of 27% versus 87% respectively 6
• A comparison of permethrin 5% and ivermectin found that twice application of permethrin with a 1-week interval was superior to a single dose of ivermectin, with permethrin-treated patients recovering earlier 7

Administration and Efficacy

• Permethrin is typically applied as a 5% cream, with a single application or repeated applications as needed 3, 4
• The cream should be left on the skin for 24 hours and repeated 7-10 days later 4
• Permethrin has been shown to be effective in treating scabies, with cure rates ranging from 61.8% to 92.5% in different studies 3, 4, 7
• However, the efficacy of permethrin may be reduced in cases where the scabies mites have developed resistance to the treatment 6