The α-adrenoceptor blocking effect of indoramin on human isolated smooth muscle

The pharmacological effects of indoramin, a new hypotensive drug, were studied on human isolated smooth muscle preparations. Indoramin was shown to have a potent α-adrenoceptor blocking activity on specimens of colon, ileum and vein. The blockade fulfilled the established criteria for competitive antagonism of noradrenaline. The mean pA2 values were 6ṁ57 for the circular muscle of the colon, 6ṁ91 for longitudinal muscle of the colon, 6ṁ64 for longitudinal muscle of the ileum and 6ṁ58 for saphenous vein. Indoramin (10−3m) did not reduce acetylcholine-induced contractions of the longitudinal muscle of the colon and ileum.