Effect of cimetropium bromide and other antispasmodic compounds on in vitro guinea-pig gallbladder.

The effect of cimetropium bromide, a new antimuscarinic compound, on bethanechol- and electrically-induced contractions was studied on isolated guinea-pig gallbladder. Atropine and two other widely employed antispasmodics (i.e., rociverine and octylonium bromide) were employed as reference compounds. Cimetropium and atropine proved to be competitive antimuscarinics, their pA2 being 7.77 +/- 0.14 and 8.31 +/- 0.14, respectively. On the contrary, rociverine displayed a dual effect being a competitive antagonist at low (up to 10(-5) mol/l) and a mixed one at high (greater than 10(-5) mol/l) concentrations. When tested against bethanechol- and electrically-induced contractions, all the compounds, with the exception of octylonium bromide, showed a concentration-dependent relaxant effect. In both experimental conditions, the potency of cimetropium was of the same order of magnitude as that of atropine and 150-200 times higher than that of rociverine. These data, together with the reported activity on human gallbladder in vivo and the well known involvement of cholinergic system in the control of gallbladder motility, could represent the rationale for the clinical use of cimetropium in the treatment of biliary colics as well as spasms of biliary tree.