The assessment of the beta-blocking activity of urapidil: a new method

Urapidil is an antihypertensive vasodilator agent whose pharmacological action in man has not yet been fully defined. We have assessed the beta blocking activity of urapidil 15 mg and 30 mg i.v. in a single blind study of 10 healthy male volunteers. Urapidil at plasma concentrations in the same range as those shown to have antihypertensive affect did not significantly attenuate the chronotropic effect of isoproterenol. Propranolol 5 mg iv, the positive control, significantly shifted the isoproterenol dose-response curve to the right. We describe a new method of analyzing incomplete dose response curves whereby a linear terminal segment can be reproducibly defined.