 | This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these messages)
Needs more citations. Includes a large table which needs to be turned into prose or removed. |
| Muscarinic acetylcholine receptor antagonist | |
|---|---|
| Drug class | |
 Skeletal formula of scopolamine, a nonselective antagonist of the muscarinic receptors | |
| Class identifiers | |
| Synonyms | Muscarinic acetylcholine receptor antagonist; Antimuscarinic; Anti-muscarinic; mACh antagonist; mAChR antagonist; Muscarinic antagonist; Antimuscarinic agent; Antimuscarinic drug; Antimuscarinic medication |
| Use | Allergies, asthma, atrial fibrillation with bradycardia,[1] motion sickness, Parkinson's disease, etc. |
| ATC code | V |
| Biological target | Muscarinic acetylcholine receptors |
| External links | |
| MeSH | D018727 |
| Legal status | |
| In Wikidata | |
A muscarinic acetylcholine receptor antagonist, also simply known as a muscarinic antagonist or as an antimuscarinic agent, is a type of anticholinergic drug that blocks the activity of the muscarinic acetylcholine receptors (mAChRs). The muscarinic receptors are proteins involved in the transmission of signals through certain parts of the nervous system, and muscarinic receptor antagonists work to prevent this transmission from occurring. Notably, muscarinic antagonists reduce the activation of the parasympathetic nervous system. The normal function of the parasympathetic system is often summarised as "rest-and-digest", and includes slowing of the heart, an increased rate of digestion, narrowing of the airways, promotion of urination, and sexual arousal. Muscarinic antagonists counter this parasympathetic "rest-and-digest" response, and also work elsewhere in both the central and peripheral nervous systems.
Drugs with muscarinic antagonist activity are widely used in medicine, in the treatment of low heart rate, overactive bladder, respiratory problems such as asthma and chronic obstructive pulmonary disease (COPD), and neurological problems such as Parkinson's disease and Alzheimer's disease. A number of other drugs, such as antipsychotics and the tricyclic family of antidepressants, have incidental muscarinic antagonist activity which can cause unwanted side effects such as difficulty urinating, dry mouth and skin, and constipation.
Acetylcholine (often abbreviated ACh) is a neurotransmitter whose receptors are proteins found in synapses and other cell membranes. Besides responding to their primary neurochemical, neurotransmitter receptors can be sensitive to a variety of other molecules. Acetylcholine receptors are classified into two groups based on this:
Most muscarinic receptor antagonists are synthetic chemicals; however, the two most commonly used anticholinergics, scopolamine and atropine, are belladonna alkaloids, and are naturally extracted from plants such as Atropa belladonna, the deadly nightshade. The name "belladonna", Italian for "beautiful lady", is thought to derive from one of the antimuscarinic effects of these alkaloids: they were used by women for cosmetic purposes, to promote dilation of the pupils.[2]
Muscarinic antagonist effects and muscarinic agonist effects counterbalance each other for homeostasis.
Certain muscarinic antagonists can be classified into either long-acting muscarinic receptor antagonists (LAMAs) or short-acting muscarinic receptor antagonists (SAMAs), depending on when maximum effect occurs and for how long the effect persists.[3]
- ^ "Hyoscyamine Subs for Pacemaker in Afib with Bradycardia". www.medpagetoday.com. May 14, 2018.
- ^ "Belladonna: MedlinePlus Supplements". medlineplus.gov. Retrieved 2020-08-13.
- ^ Ritter, James (2020). Rang and Dale's pharmacology. R. J. Flower, Graeme Henderson, Yoon Kong Loke, David J. MacEwan, H. P. Rang (9th ed.). Edinburgh. p. 377. ISBN 978-0-7020-8060-9. OCLC 1081403059.
{{cite book}}: CS1 maint: location missing publisher (link)