Overview
Permethrin is a topical medication used as a first-line treatment for scabies (a skin infestation by mites) and pediculosis (head lice or pubic lice).

Mechanism of Action
It is a synthetic pyrethroid that acts as a neurotoxin to insects. It disrupts the sodium channel current in the nerve cell membranes of parasites, leading to delayed repolarisation, paralysis, and eventually the death of the mites or lice and their eggs.

Dosage and Administration
For scabies, a 5% cream is applied thoroughly from the neck down to the soles of the feet and left on for 8 to 14 hours before being washed off. For head lice, a 1% lotion is applied to washed, towel-dried hair, left on for 10 minutes, and then rinsed out.

Side Effects
Common side effects include temporary itching, stinging, or redness at the application site. Mild burning or a tingling sensation may also occur immediately after application.

Contraindications
Contraindicated in individuals with known hypersensitivity to permethrin, any of its components, or other pyrethroids/pyrethrins. Avoid contact with eyes and mucous membranes.