Cholinergic blocking drugs are a group of drugs that block the action of acetylcholine (ACh), a neurotransmitter, in synapses of the cholinergic nervous system.[1] They block acetylcholine from binding to cholinergic receptors, namely the nicotinic and muscarinic receptors.
These agents have broad effects due to their actions in nerves located vastly over the body. These nerves include motor nerves in somatic nervous system which innervate skeletal muscles as well as nerves in the sympathetic and parasympathetic nervous systems.[1] Organs that receive innervations from these systems include exocrine glands, heart, eyes, gastrointestinal tract etc. Antimuscarinic and antinicotinic agents can increase heart rate, inhibit secretions, and gastrointestinal motility.[1][2]
Naturally occurring antimuscarinics were found in alkaloids from Belladonna (Solanaceae) plants. They were used as deadly poison and pupil-dilating cosmetics. While curare, the naturally occurring antinicotinics derived from Chondrodendron and Strychnos, was a poison used by South American Indians for hunting.[1][3][4]
According to their site of actions, cholinergic blocking drugs can be classified into two general types — antimuscarinic and antinicotinic agents.[1] Antimuscarinic agents (also known as muscarinic antagonists), including atropine and hyoscine, block acetylcholine at the muscarinic acetylcholine receptors. Antinicotinic agents (also known as ganglionic blockers, neuromuscular blockers), including tubocurarine and hexamethonium, block acetylcholine action at nicotinic acetylcholine receptors. Their effects are based on the expression of corresponding receptors in different parts of the body.
There are many adverse effects, interactions and contraindications for antinicotinic and antimuscarinic agents. Adverse effects include hypotension, dry mouth, dry eyes etc. They interact with grapefruit juice and various medications, e.g. warfarin, metoclopramide. Therefore, cautions should be exercised and advice from medical professionals should be sought before using medications.
- ^ a b c d e Patrick G (2019-10-10). "Introduction". Introduction, Medicinal Chemistry. Taylor & Francis. pp. 2–3. doi:10.1201/9780429188572-1. ISBN 978-0-429-18857-2. S2CID 243582955.
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