antimuszkarin

Antimuscarinic, or antimuscarinic agent, refers to a substance that antagonizes muscarinic acetylcholine receptors (M1–M5), thereby inhibiting actions of the parasympathetic nervous system. They are a subset of anticholinergic drugs used in medicine to counteract excess acetylcholine signaling.

Mechanistically, most antimuscarinics act as competitive antagonists at muscarinic receptors. By blocking M receptors in smooth muscle, glands, the heart, and in the central nervous system, they reduce glandular secretions, relax smooth muscle, increase heart rate, and, for lipophilic agents, may influence cognitive function and central processing.

Common indications include pupil dilation for eye examinations (mydriasis) and cycloplegia, preoperative reduction of secretions, treatment of bradycardia, overactive bladder (oxybutynin, tolterodine, solifenacin), and management of COPD or asthma (ipratropium, tiotropium). They are also used as adjuncts in Parkinson’s disease (benztropine, trihexyphenidyl) to reduce tremor and rigidity. Scopolamine is employed for motion sickness and postoperative nausea. Some agents are topical or inhaled, offering targeted effects with fewer systemic side effects. In poisonings, antimuscarinics are used to counteract muscarinic overstimulation; in organophosphate poisoning, atropine is part of the antidotal regimen.

Adverse effects reflect reduced parasympathetic activity: dry mouth, blurred vision and photophobia, constipation, urinary retention, tachycardia, and cognitive disturbances, particularly in the elderly. They should be used with caution in patients with angle-closure glaucoma, benign prostatic hyperplasia, dementia, or GI or urinary obstructions. Historically derived from plants such as belladonna and henbane, these drugs remain widely used but require careful dosing and monitoring.