A new beta 2-adrenoceptor agonist with alpha 1-adrenoceptor blocking properties.

The phenylethanolamine D2343 exhibits a dualistic adrenoceptormediated effect, i.e, a beta-agonistic effect combined with an alpha-antagonistic one. Tracheal smooth muscles and heart preparations were used to gauge the agonistic effect of adrenergic beta-receptors. Rabbit aorta and rat vas deferens were used to determine the alpha-adrenoceptor blocking activity. The beta-adrenoceptor activity of D2343 was classified as beta 2-type with about the same efficacy as the beta 2-selective terbutaline on tracheal muscle. The effect on isolated heart preparations was greater than that produced by terbutaline. The alpha-receptor blocking capacity was directed against the alpha 1-receptor type and was of nearly the same potency as for phentolamine.