Anticholinergic Drugs

Introduction & terminology

• Cholinergic agonists — (cholinomimetics, parasympathomimetics) reproduce the actions of acetylcholine (ACh) — either directly on cholinoceptors or indirectly by raising ACh via cholinesterase inhibition.
• Anticholinergic drugs — block ACh at muscarinic receptors on autonomic effectors and in the CNS (synonyms: antimuscarinic, atropinic, parasympatholytic). Nicotinic blockers are separately termed ganglion blockers and neuromuscular blockers.
• Atropine — is the prototype antagonist — highly selective for muscarinic over nicotinic receptors; all anticholinergics are competitive, surmountable antagonists whose block is overcome by raising the agonist concentration.
• The topic spans both faces of the same receptor target — the muscarinic agonists (choline esters + cholinomimetic alkaloids) and the antagonists (belladonna alkaloids + synthetic/semisynthetic substitutes).