anticholinergic

Anticholinergic refers to drugs and substances that block acetylcholine at muscarinic receptors, reducing parasympathetic activity. They are competitive antagonists of muscarinic acetylcholine receptors (M1–M5). Some cross the blood–brain barrier (tertiary amines) producing central effects, while others are quaternary ammonium compounds that act primarily peripherally.

Medical uses include treating bradycardia, reducing secretions before anesthesia, and managing overactive bladder. They are also used to dilate pupils and paralyze accommodation for eye exams, to reduce motion sickness (scopolamine), and, in several agents, to relieve tremor in Parkinson's disease. Inhaled forms (ipratropium, tiotropium) are bronchodilators for COPD and, to a lesser extent, asthma.

Common anticholinergics include atropine, scopolamine, ipratropium, tiotropium, oxybutynin, tolterodine, solifenacin, trospium, benztropine, and trihexyphenidyl. They vary in selectivity and CNS penetration; peripheral quaternaries have fewer central effects.

Typical adverse effects reflect reduced parasympathetic tone: dry mouth, constipation, urinary retention, blurred vision, and tachycardia. Central effects—confusion, delirium, and memory impairment—are especially risky for older adults, contributing to anticholinergic burden and cognitive decline. Interactions with other anticholinergic drugs or sedatives can compound toxicity.

The term originates from belladonna alkaloids; atropine is a classic example. While widely used in medicine, anticholinergics require caution in the elderly and in individuals with glaucoma, bowel obstruction, or urinary retention.