Permethrin for lice

Examples

Permethrin is available over-the-counter in different strengths.

Generic Name	Brand Name
permethrin 1%	Kwellada-P Creme Rinse, Nix
permethrin 5%	Kwellada-P Lotion, Nix Dermal Creme

Permethrin 1% (Kwellada-P Creme Rinse or Nix) is used to treat head lice. Instructions for use:

• Wash and towel dry the hair.
• Apply enough of the creme rinse to the hair to saturate the hair and scalp.
• Leave the creme rinse on for 10 minutes.
• Rinse the creme rinse off with water.
• Avoid getting permethrin in the eyes. Although the product is not known to be harmful to the eyes, rinse the eyes well with water if the creme rinse gets into them.
• Experts do not agree whether it is necessary to comb the nits out of the hair after treatment with Nix. You may wish to do so for cosmetic reasons.

When permethrin is used to treat pubic lice, a second treatment is recommended in 7 to 10 days. Most experts advise a second treatment 7 to 10 days after the first treatment for head lice.¹

Permethrin 5% (Kwellada-P Lotion or Nix Dermal Creme) is applied to the skin or hair, left on for 8 to 14 hours, and then rinsed off. Permethrin 5% is available at most pharmacies behind the counter.

How It Works

Permethrin kills lice and their eggs (nits). Permethrin continues to kill lice and eggs for at least 2 weeks after it has been rinsed off.

Why It Is Used

Permethrin creme rinse (Kwellada-P Creme Rinse or Nix) is a common first choice for treating head lice.

Permethrin 5% (Kwellada-P Lotion or Nix Dermal Creme) may be used to treat cases of lice that persist after treatment with other products.

How Well It Works

Permethrin is very safe and effective. But resistance to permethrin has been reported in many countries (such as United Kingdom and United States).^{1, 2} If resistance to permethrin is noted, your health professional can recommend other treatment (such as pyrethrin) or a combination of treatments, such as permethrin cream along with trimethoprim sulfamethoxazole (Novo-Trimel).

Side Effects

Permethrin is very safe and has few side effects. Itching, burning or stinging, or temporary redness of the skin may occur. If these side effects persist, call your health professional.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Permethrin is easy to use, safe, and usually effective.

Overuse of lice medications (such as reapplying the creme rinse or cream when only a single use is recommended) can irritate the skin and may increase the risk of side effects from some products. It is common for itching to persist for 7 to 10 days after treatment. Itching is not a reason to treat the person again.

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Author:	Debby Golonka, MPH Carrie Henley	Last Updated: February 13, 2007
Medical Review:	Anne C. Poinier, MD - Internal Medicine Michael J. Sexton, MD - Pediatrics Thomas Emmett Francoeur, MDCM, CSPQ, FRCPC - Pediatrics
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