Zamifenacin is an antagonist of M3 muscarinic acetylcholine receptors (Ki = 10 nM for the human receptor).1 It is selective for M3 over M1, M2, M4, and M5 receptors in radioligand binding assays using cells expressing recombinant human receptors (Kis = 55, 153, 68, and 34 nM, respectively). Zamifenacin inhibits cholecystokinin-induced small bowel motility (ED50 = 0.9 mg/kg) but does not increase heart rate (ED150 = 80.0 mg/kg) in dogs.2
1.Moriya, H., Takagi, Y., Nakanishi, T., et al.Affinity profiles of various muscarinic antagonists for cloned human muscarinic acetylcholine receptor (mAChR) subtypes and mAChRs in rat heart and submandibular glandLife Sci.64(25)2351-2358(1999) 2.Wallis, R.M.Pre-clinical and clinical pharmacology of selective muscarinic M3 receptor antagonistsLife Sci.56(11-12)861-868(1995)