Assessment of selective beta-adrenoceptor blockade in man.

1. Selective antagonism of the cardiac beta(1)-adrenoceptors has been studied in normal human volunteers.2. Practolol and UK 6558 produced greater antagonism of the chronotropic and inotropic responses to i.v. isoprenaline than of the vasodilator response to either i.v. or intra-arterial isoprenaline. A third drug, M&B 17,803A, produced non-selective beta-adrenoceptor blockade in 2 of 3 subjects studied.3. Practolol, UK 6558 and M&B 17,803A, produced an attenuation of the responses to Valsalva's manoeuvre.4. A substantial reduction in blood pressure was seen in 3 of 4 normotensive subjects given UK 6558.