Effects of labetalol and propranolol on blood pressure at rest and during isometric and dynamic exercise

The influence of intravenous labetalol and propranolol on the blood pressure response to isometric and dynamic exercise was examined in a double blind study in eight, young, normotensive volunteers. Effects were recorded after propranolol 7.5, 15 and 30 mg i. v., and after labetalol 30, 60 and 120 mg i. v. In control experiments saline was administered. Mean blood pressure rose with successive handgrip tests following saline and propranolol, but not after labetalol, and the difference was significant. The total dose of each drug produced the same reduction in heart rate during sub-maximal bicycle exercise. The exercise-induced systolic blood pressure response did not differ between the drugs.