The patient is treated for head lice with permethrin (NIX). The nurse practitioner may recommend retreating with the same product in 9 days because: Select one:

Head lice infestation, or pediculosis capitis, is commonly treated with topical pediculicides such as Permethrin (Nix). Treatment aims to eliminate live lice and prevent reinfestation from newly hatched eggs. Although permethrin is highly effective against active lice, some eggs may survive the initial treatment. A second application is often recommended after several days to target lice that hatch after the first dose. Rationale: A. Redosing is not done to prevent scabies infection because head lice and scabies are caused by different parasites and require different treatment approaches. Permethrin (Nix) used for head lice is intended specifically for pediculosis capitis, not for preventing scabies transmission. The repeat dose is related to lice management, not mite infestation. B. Permethrin is pediculicidal, meaning it effectively kills live lice by disrupting sodium channel function in the parasite’s nerve cell membranes, leading to paralysis and death. This is why it is considered a first-line therapy for head lice. The problem is not failure to kill live lice, but rather incomplete destruction of the eggs. C. Over-the-counter permethrin is considered effective and does not require redosing because it is too weak. The need for retreatment is based on the life cycle of lice rather than medication strength. Even with proper use, surviving nits may hatch later, making a second treatment necessary to fully interrupt reinfestation. D. Permethrin is not fully ovicidal, meaning it may not destroy all lice eggs (nits) during the first treatment. Eggs that survive can hatch several days later and lead to reinfestation if not addressed. Retreatment around day 7 to 9 targets these newly hatched lice before they mature and lay additional eggs, ensuring complete eradication.