Snapshot A 16-year-old girl presents to an urgent care clinic for an itchy rash which worsens at night. On physical exam, there are burrows in her finger web spaces bilaterally and areas of excoriation where she scratches herself at night. There are also erythematous papules on her wrists. A skin scraping with mineral oil prep shows mites under microscopy. She is instructed to use topical permethrin and to sterilize all laundry. Her family members need to receive treatment as well. (Scabies 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