Snapshot A 5-year-old girl comes home from school reporting itching. Her mom notices that she is scratching her hair. She finds out that other children at the school are suffering from similar symptoms. They present to the pediatrician's office, where a careful examination shows viable nits 0.5 cm away from base of the hair shaft. She is prescribed topical permethrin. (Pediculus capitis infection) Introduction Drugs permethrin topical as lotion or shampoo malathion topical as cream or shampoo lindane topical as lotion, cream, or shampoo Clinical use Sarcoptes scabiei (scabies) Pediculus capitis (lice) Pthirus pubis (lice) Permethrin Mechanism of action inhibits deactivation of sodium channels, leading to neuronal membrane depolarization and paralysis in the louse or mite Adverse effects skin irritation burning sensation Malathion Mechanism of action inhibits acetylcholinesterase Adverse effects hypersensitivity skin irritation Lindane Mechanism of action inhibits GABA channels, leading to neurotoxicity in the louse or mite Clinical use not indicated in crusted scabies typically not used as a first-line agent Adverse effects skin irritation anxiety