Effects of labetalol on plasma renin, aldosterone, and catecholamines in hypertensive patients.

We studied the effects of labetalol, an alpha- and beta-adrenoceptor antagonist, on maximum exercise heart rate and on plasma renin, aldosterone, noradrenaline, and adrenaline levels at rest and during exercise in hypertensive patients. The dose of labetalol was doubled weekly from 0.3 to 2.4 g per day. The maximum exercise heart rate fell significantly during labetalol treatment, and there was a significant correlation between exercise tachycardia and the dosage of labetalol. Plasma renin activity and aldosterone concentration at rest decreased during treatment with labetalol. The exercise-induced increase in plasma renin activity was reduced by labetalol. Labetalol did not cause any significant changes in plasma noradrenaline and adrenaline at rest or during exercise.