Effects of combined alpha- and beta-receptor blockade on peripheral circulation in essential hypertension.

1. Six weeks' treatment with labetalol (600 mg/day) significantly reduced systolic and diastolic blood pressures in 24 patients with essential hypertension. There was a small but not significant decrease in heart rate. 2. After 6 weeks of therapy mean digital arterial blood flow at rest and during reactive hyperaemia had increased by 26%. 3. In nine essential hypertensive patients intravenous administration of 100 mg of labetalol caused prompt and striking reductions of systolic and diastolic blood pressures without significant changes in heart rate. There was a consistent and significant increase in peripheral blood flow by 32% 5 min after administration of the drug. 4. Antagonism of alpha-receptors in addition to beta-receptors might improve peripheral arterial blood flow while achieving antihypertensive control. Thus labetalol, owing to its favourable haemodynamic effects, may have advantages over conventional pure beta-receptor-blocking agents.