scopolamine

Scopolamine, also called hyoscine, is a tropane alkaloid with antimuscarinic properties used in medicine to treat nausea and motion sickness. It occurs naturally in several Solanaceae plants, including deadly nightshade (Atropa belladonna), jimson weed (Datura stramonium), and henbane (Hyoscyamus niger).

Pharmacology: Scopolamine acts as a competitive antagonist of muscarinic acetylcholine receptors (M1–M5). It crosses the blood–brain barrier, producing central nervous system effects such as drowsiness or sedation at higher doses. Peripherally, it reduces secretions and modulates gastrointestinal and vestibular activity, contributing to antiemetic and anti-vertigo effects.

Medical uses: It is employed to prevent postoperative nausea and vomiting and to treat motion sickness and vertigo. It is available in oral tablets, injectable solutions, and as a transdermal patch that delivers a steady dose over several days to reduce nausea for travel or postoperative care.

Safety and adverse effects: Common anticholinergic effects include dry mouth, blurred vision, photophobia, constipation, urinary retention, tachycardia, and dizziness. Central effects can include confusion or sedation, particularly in older adults. Scopolamine is contraindicated in narrow-angle glaucoma and should be used with caution in patients with delirium, myasthenia gravis, or urinary retention. Interactions occur with other anticholinergic drugs, CNS depressants, and alcohol. It is usually used during pregnancy only if clearly needed (pregnancy category C).

Overdose or poisoning can cause delirium, hallucinations, and coma. Treatment is supportive care and, in specialized settings, antidotal therapy with physostigmine under medical supervision. Regulatory status varies by country; scopolamine is generally prescription-only.