Effect of labetalol on exercise tolerance and double product in mild to moderate essential hypertension.

Maximal exercise capacity after control of resting blood pressure with labetalol was studied in nine hypertensive men aged 34 to 69 years (average 52 years). Subjects exercised to exhaustion on an upright cycle ergometer with workload increased as a step function by 25 watts every three minutes, both before and after control of blood pressure was obtained. Mean exercise capacity expressed as total time of exercise until exhaustion was 936 seconds prior to control of the resting blood pressure and 884 seconds (no significant difference) after control of resting blood pressure with labetalol. Double product at peak exercise fell from 254 X 10(2) mm Hg beats per minute prior to blood pressure control to 183 X 10(2) mm Hg beats per minute (p = 0.006) after control of blood pressure with labetalol. The difference in the means of resting heart rate and both peak blood pressure and peak heart rate with exercise were all statistically significant after control of blood pressure with labetalol. These findings suggest that labetalol has an ideal exercise profile affording a cardioprotective effect by decreasing double product but without sacrificing exercise capacity.