Generic Name: permethrin

Brand Names: Nix, ElimiteActicin

Drug Class: Scabicidal Agents; Pediculicides, Topical

What is permethrin, and what is it used for?

Permethrin is a topical medication used to treat scabies and head lice infestations.

Permethrin is available over the counter and by prescription as a topical cream, liquid, and lotion which may be applied on the affected areas of the scalp or skin. Permethrin must be used a few times until all the lice eggs (nits) hatch and are eliminated because it can kill live lice but cannot kill unhatched eggs.

Permethrin is a synthetic pyrethroid pesticide, manufactured with a compound that is similar to the natural pyrethrin found in the flowers of pyrethrum plants such as chrysanthemum. Pyrethrin is a natural pesticide that contains six chemicals that are toxic to insects and are commonly used to control home and garden pests such as mosquitoes, flies, fleas, and ants.

Permethrin is neurotoxic to scabies mites and head lice, killing them by paralyzing the nerves and the respiratory muscles of the parasites. Permethrin interferes with the influx of sodium ions in the parasitic nerve cell membranes, depolarizing the nerve cells, which results in paralysis and death of these parasites.

Warnings

  • Do not use permethrin if you are hypersensitive to pyrethroid medications, pyrethrin, permethrin or any of its components
  • Do not apply permethrin to infants younger than 2 months old
  • Permethrin may temporarily exacerbate the redness, swelling, and itching from the parasite infestation
  • Permethrin may cause breathing difficulty or asthmatic attack in patients with ragweed allergies; use with caution

What are the side effects of permethrin?

Common side effects of permethrin include:

  • Local discomfort (scalp)
  • Rash in scalp
  • Itching (pruritus)
  • Localized burning or numbness
  • Localized swelling (edema)
  • Tingling of the skin
  • Stinging of the skin
  • Redness of the skin (erythema)

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

What are the dosages of permethrin?

Cream

  • 5%

Liquid

  • 1%

Lotion

  • 1%

Adult:

Scabies

  • Cream: Apply from head to toe, leave on for 8-14 hours, rinse; may reapply in 7 days if live mites reappear
  • The single application is usually curative

Head Lice and Nits (Eggs)

  • Lotion/cream rinse/liquid: apply to washed hair, leave on 10 minutes, rinse and comb out nits and eggs; may repeat in 7 days if lice or nits still present
  • The single application is usually curative

Pediatric:

Scabies and Head Lice

Children under 2 months

  • Safety and efficacy not established

Children over 2 months

  • Scabies: Apply the cream from head to toe; leave on for 8-14 hours, rinse; may reapply in 7 days if live mites reappear; single application is usually curative
  • Head lice and nits (eggs): Apply lotion/cream/liquid to washed hair, leave on 10 minutes, rinse and comb out nits and eggs; may repeat in 7 days if lice or nits still present; a single application is usually curative

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Overdose

  • Topical use of permethrin rarely causes any toxic reaction, because there is negligible systemic absorption.
  • Excessive application has been reported to result in metabolic acidosis and neurotoxicity.
  • There is no known antidote for permethrin, toxicity may be treated with symptomatic and supportive care.

 

What drugs interact with permethrin?

  • Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.
  • Permethrin has no known severe, serious, moderate, or mild interactions with other drugs.
  • The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.
  • It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

Pregnancy and breastfeeding

  • The CDC considers permethrin as the preferred medication for pubic lice and scabies during pregnancy and while breastfeeding.
  • If a nursing mother with scabies applies permethrin directly on affected breast, she should refrain from nursing the baby until rinsing the cream off thoroughly.

What else should I know about permethrin?

  • Permethrin is for external use only
  • If permethrin is accidentally ingested, immediately seek medical help or contact Poison Control Center
  • Do not apply permethrin near the eyes or inside the nose, ear, mouth, or vagina; avoid contact with eyes
  • When self-medicating with OTC permethrin, follow the exact label instructions 
  • Do not apply permethrin on babies younger than 2 months old
  • Store safely out of reach of children

Summary

Permethrin is a topical medication used to treat scabies and head lice infestations, available over the counter and by prescription. Do not apply permethrin to infants younger than 2 months old. Common side effects of permethrin include local discomfort (scalp), rash on the scalp, itching (pruritus), localized burning or numbness, localized swelling (edema), tingling of the skin, stinging of the skin, and redness of the skin (erythema). Consult your doctor if pregnant or breastfeeding.

Treatment & Diagnosis

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Medically Reviewed on 5/17/2022
References
https://www.rxlist.com/consumer_permethrin_nix_elimite_acticin/drugs-condition.htm

https://reference.medscape.com/drug/nix-elimite-permethrin-topical-343503#0

https://www.uptodate.com/contents/permethrin-drug-information

https://www.ncbi.nlm.nih.gov/books/NBK553150/