Zamifenacin (UK-76654) is a potent gut-selective muscarinic M3 receptor antagonist. Zamifenacin significantly reduces colonic motility in irritable bowel syndrome[1].

Zamifenacin exhibits moderate oral bioavailability (mouse 26%, rat 64%, dog 100%) and Cmax (mouse 92, rat 905, dog 416 ng/mL) following oral administration (mouse 13.2, rat 20 and, dog 5 mg/kg)[2]. Zamifenacin exhibits terminal elimination half-lives (mouse 2.1, rat 6.0 and, dog 1.1 h) due to high plasma clearance (68, 35, and 39 mL/min/kg respectively) combined with large volumes of distribution (12.5, 19.0, and 3.5 L/kg respectively) following intravenous administration (mouse 5.3, rat 5.0 and, dog 1.0 mg/kg)[2]. Animal Model: Male CDl mice (mean weight 23 g)[2]

[1]. Houghton LA, et al. Zamifenacin (UK-76, 654) a potent gut M3 selective muscarinic antagonist, reduces colonic motor activity in patients with irritable bowel syndrome. Aliment Pharmacol Ther. 1997 Jun;11(3):561-8. [2]. Beaumont KC, et al. Pharmacokinetics and metabolism of Zamifenacin in mouse, rat, dog and man. Xenobiotica. 1996 Apr;26(4):459-71.