Source:http://linkedlifedata.com/resource/umls/id/C0079829
MSH: A quaternary ammonium parasympathomimetic agent with the muscarinic actions of ACETYLCHOLINE. It is hydrolyzed by ACETYLCHOLINESTERASE at a considerably slower rate than ACETYLCHOLINE and is more resistant to hydrolysis by nonspecific CHOLINESTERASES so that its actions are more prolonged. It is used as a parasympathomimetic bronchoconstrictor agent and as a diagnostic aid for bronchial asthma. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1116),NCI: The chloride salt form of methacholine, a direct-acting cholinergic muscarinic agonist with bronchoconstrictive, miotic, vasodilator, and cardiac vagomimetic activity. Methacholine chloride acts directly on the muscarinic receptors in the heart, eye, and lung, thereby producing parasympathomimetic effects.