Antihypertensive mechanism of beta-adrenoceptor antagonism--the role of beta 2-blockade.

We performed this study in order to evaluate the antihypertensive effect of selective beta 2-adrenoceptor blockade. A highly beta 2-selective antagonist (ICI 118.551) was given to 15 male patients with essential hypertension who had previously shown a lowering of blood pressure in response to beta 1-selective or nonselective beta-adrenoceptor blockade. After a four-week placebo period ICI 118.551 was given (50 or 100 mg t.i.d.) for one week (randomized, double-blind). Before and 3 h after the first dose blood pressure, central and peripheral haemodynamics were studied by impedance cardiography and forearm plethysmography respectively. Blood pressure and heart rate were also measured after one week of treatment. After acute administration of drug cardiac output fell 14% (P less than 0.001) due to a fall in heart rate from 69 to 61 beats/min (P less than 0.002). Mean arterial pressure was unchanged (112 mmHg) and total peripheral resistance increased 18% (P less than 0.01). A similar rise in forearm resistance could be seen (14%). There was no reduction in blood pressure after one week of treatment although heart rate remained significantly reduced. Selective beta 2-adrenoceptor blockade does not lower blood pressure in patients previously responding to beta 1-or beta 1/beta 2-adrenoceptor blockade.

RCT Entities:   Population Interventions Outcomes