Antihypertensive effect of propranolol at rest and during exercise

In eight patients with normal-renin, moderate hypertension, the antihypertensive effects of increasing doses of propranolol (80, 160, 320 and, in three patients, 640 mg/day, each dose for 2 weeks) were evaluated at rest and during exercise in relation to the degree of beta-adrenoceptor blockade induced. A significant decrease (11 +/- 4 mm Hg) in systolic blood pressure was found after propranolol 80 mg/day. Systolic blood pressure showed a fall of 16 +/- 4 mm Hg after 160 mg/day, but no further decrease was measured at higher doses. Diastolic blood pressure showed a significant drop (by 9 +/- 3 mm Hg) after propranolol 80 mg/day; a decrease by 12 +/- 3 mm Hg after propranolol 160 mg/day, but no further decreases at higher doses. PRA and the rise of systolic blood pressure during bicycle exercise were suppressed to a similar extent by propranolol 80 ng and the higher doses. At 80 mg daily exercise tachycardia was reduced by 18%, at 160 mg by 28%, and at the 2 higher doses by 32%. These results suggest that relatively low doses of propranolol (80-160 mg daily) induce most of the antihypertensive effect of propranolol not only at rest but also during exercise. Complete cardiac chronotropic beta-adrenoceptor blockade may not be necessary for the full hypotensive effect.