Hyoscin

Hyoscin, often used as an alternative spelling of hyoscine (also known as scopolamine), refers to a tropane alkaloid with antimuscarinic (anticholinergic) properties used in medicine. It exists in several salt forms, including hyoscine hydrobromide and hyoscine butylbromide. Hyoscine hydrobromide is a centrally acting antimuscarinic with antiemetic and sedative effects, used to prevent and treat motion sickness and postoperative nausea and vomiting, and in some regimens to provide preoperative sedation. Hyoscine butylbromide is a quaternary ammonium compound that poorly penetrates the central nervous system and acts mainly peripherally to relieve smooth muscle spasm; it is used for gastrointestinal, biliary, and urinary tract cramping and related pains.

Mechanism of action involves competitive antagonism of muscarinic acetylcholine receptors (M1–M5), reducing parasympathetic activity. This leads to decreased secretions, reduced gastrointestinal and biliary tract motility, and, in the eye, pupil dilation and cycloplegia as side effects. The peripheral form hyoscine butylbromide mainly produces antispasmodic effects with fewer central nervous system effects.

Common indications include prevention of motion sickness, prevention of postoperative nausea and vomiting, and treatment of irritable bowel-related cramps; peripheral spasmolysis is used for abdominal colic, biliary colic, and bladder spasm. Side effects are typical anticholinergic effects: dry mouth, blurred vision, constipation, urinary retention, tachycardia, confusion, and dizziness, especially in the elderly. Contraindications include narrow-angle glaucoma, intestinal obstruction or paralytic ileus, severe urinary retention, and certain cardiac conditions; use requires caution with elderly patients and in those taking other anticholinergic agents.