BMA Concise Guide to Medicine & Drugs

Permethrin

Brand name Lyclear

Used in the following combined preparations None

QUICK REFERENCE

Drug group Drug to treat skin parasites

Overdose danger rating Low

Dependence rating Low

Prescription needed No

Available as generic Yes

GENERAL INFORMATION

Permethrin is an insecticide used to treat pubic lice (but not head lice) and scabies infestations. The drug works by interfering with the nervous system of the parasites, causing paralysis and death. Permethrin is less toxic to humans than some of the other types of insecticide, although it is toxic to some animals, such as cats.

Permethrin is applied topically as a cream to treat pubic lice and scabies infestations. It should not be used on broken or infested skin. In children and elderly people, the entire body surface, including the face, scalp, neck, and ears, may have to be covered; adults are treated from the neck downwards. For pubic lice, the entire body should be treated and the permethrin left on overnight. A second treatment seven days later is needed. For both pubic lice and scabies, all family members should be treated at the same time, to prevent recontamination, and the process repeated after a week.

There are signs that the parasites are developing resistance to permethrin. If the drug does not work for you, your pharmacist should be able to suggest an alternative treatment (e.g. malathion).

Permethrin is also an ingredient of some insect repellents used to impregnate clothing and mosquito nets in malarial regions.

INFORMATION FOR USERS

Follow instructions on the label. Call your doctor if symptoms worsen.

How taken/used Cream.

Frequency and timing of doses Once only, repeating after 7 days (2 years and over); under specialist supervision only (infants and children under 2 years). Avoid contact with eyes and broken or infected skin.

Dosage range As directed.

Onset of effect Public lice Wash off after 12–24 hours. Scabies Wash off after 8–12 hours.

Duration of action Until washed off.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Timing of the second application is not rigid; use as soon as you remember.

Stopping the drug Not applicable.

Exceeding the dose An occasional extra application is unlikely to cause problems. If the drug is accidentally swallowed, take emergency action.

POSSIBLE ADVERSE EFFECTS

In general, permethrin is well tolerated on the skin, although mild irritation is common, with stinging, itchiness, and redness. Rarely, a rash may develop. Discuss with your doctor if any of these effects are severe.

INTERACTIONS

Corticosteroids Treatment of eczema-like reactions to permethrin with these drugs may lower the immune response to the mites and should not be given.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You are taking other medicines.

Pregnancy Safety not established. Discuss with your doctor.

Breast-feeding Safety not established. Discuss with your doctor.

Infants and children Under specialist supervision only under 2 years. No special problems in older children.

Over 60 No special problems, but consult your doctor or a health professional.

Driving and hazardous work No special problems.

Alcohol No special problems.

PROLONGED USE

Permethrin should not be used topically for prolonged periods; it is intended for intermittent use only. Prolonged use of permethrin to impregnate clothing and netting is not known to cause serious toxic effects.