scopolamin

Scopolamine, also known as hyoscine, is a tropane alkaloid with antimuscarinic (anticholinergic) properties. It is found in several Solanaceae plants, including Hyoscyamus niger (henbane), Datura stramonium (jimson weed), and Atropa belladonna (deadly nightshade). Scopolamine acts as a competitive antagonist at muscarinic acetylcholine receptors (M1–M5), reducing parasympathetic activity and influencing smooth muscle, secretory glands, and the central nervous system.

Medical uses include prevention of motion sickness and postoperative nausea and vomiting, often via a transdermal patch that provides a sustained release over about 72 hours. In ophthalmology, scopolamine is used as a cycloplegic and mydriatic agent to relax the ciliary muscle and dilate the pupil. It can also be employed as part of preanesthetic regimens to decrease saliva and airway secretions. Pharmacologic salt forms include scopolamine hydrobromide and scopolamine butylbromide (hyoscine butylbromide), the latter used as an antispasmodic for gastrointestinal cramps.

Pharmacology and pharmacokinetics: scopolamine is lipophilic and crosses the blood–brain barrier, contributing to central nervous system effects such as drowsiness, confusion, and amnesia at higher doses. Onset and duration vary by route of administration, with transdermal delivery offering a slow, continuous effect.

Adverse effects and safety: common side effects include dry mouth, blurred vision, dizziness, drowsiness, and tachycardia; urinary retention; and cognitive disturbance, particularly in older adults. At toxic levels, it can cause delirium, agitation, and seizures. Interactions with other anticholinergics, antihistamines, and alcohol can amplify effects. Caution is advised in glaucoma and certain cardiovascular conditions. Scopolamine has also been reported in misuse as a incapacitating agent, underscoring the importance of controlled use.