cis(-)-2,3-Dihydro-3-(4-methylpiperazinylmethyl)-2-phenyl-1,5- benzothiazepin-4(5H)-one monohydrochloride and its butylbromide as M1-receptor antagonists.

Selectivity of cis(-)-2,3-dihydro-3-(4-methylpiperazinylmethyl)-2-phenyl-1,5-b enzothiazepin-4 (5H)-one monohydrochloride (BTM-1086) and its butylbromide (BTM-1073) to subtypes of muscarinic receptor, M1-and M2-receptors were tested, using pirenzepine, a M1-selective antagonist and atropine, a nonselective antagonist as reference drugs. Like pirenzepine, BTM-1086 and BTM-1073 were M1-selective antagonists. BTM-1086 was most selective among the test drugs. BTM-1073, a butylbromide of BTM-1086 was more potent than BTM-1086 in antimuscarinic activity tested on the isolated ileal longitudinal muscle, suggesting that quarternarization increased selectivity to M2-receptor but not to M1-receptor.