Cimetropium Bromide is a mAChR antagonist used for long-term treatment of irritable bowel syndrome.

Cimetropium reduces the release of labeled acetylcholine (ACh) elicited by electrical field stimulation, particularly when muscarinic autoinhibition is blocked, as observed in superfusion experiments using preparations preloaded with labeled choline [2]. Furthermore, it exhibits a powerful antimuscarinic action by inhibiting the contraction of longitudinal muscle preparations. As a competitive antagonist, Cimetropium Bromide effectively counteracts muscarinic-mediated contractions in isolated colonic preparations from various species, demonstrating affinity values (pA2) between 7.41 and 7.82 [1].

Cimetropium Bromide (10-100 μg/kg) counteracts colonic motor response to neostigmine administration (ID50: 27.9 μg/kg); both tonic and phasic components of contractile response are affected. Cimetropium is a potent inhibitor of large bowel motility evoked by both exogenous and endogenous stimuli when administered intravenously to conscious dogs provided with a colonic Thiry fistula. In a comparable range of doses (3-100μg/kg), the drug inhibits motor activity elicited by intraluminal distension [1].