methacholine
/mɛθəˈkəʊliːn/Pharmacology
noun
A choline derivative with parasympathomimetic activity that can induce bronchoconstriction in asthmatics and is used in tests of airway responsiveness; O-acetyl-β-methylcholine, C8H18ClNO2.
Origin
1940s; earliest use found in Science. From meth- (in methyl: see note s.v. meth-) + -a- connective + choline.