Antihypertensive effect and degree of beta-adrenoceptor blockade after short-term and semi-chronic propranolol...

In patients with normal-renin, mild (n = 6) or moderate (n = 6) hypertension, the antihypertensive effects of propranolol (80 mg/day) for 1 day or for 2 weeks were evaluated in relation to the degree of beta-adrenoceptor blockade induced. A significant and similar fall in systolic blood pressure was observed after 1 day and 2 weeks on propranolol in both groups of patients. In contrast, diastolic blood pressure showed only a minor decrease after 1 day of therapy (-2 +/- 2 and -3 +/- 1 mm Hg) but a significant drop (-7 +/- 3 and -9 +/- 3 mm Hg) after 2 weeks in the mild and moderate hypertension groups, respectively. Plasma propranolol levels and decreases in resting heart rate and PRA were similar after 1 day and 2 weeks of treatment. Isoprenaline dose-response curves for systolic and diastolic blood pressure, heart rate and PRA showed similar parallel shifts after 1 day and 2 weeks of treatment. The effect of graded bicycle exercise on these parameters were also similarly blunted. These results indicate that over time, systolic blood pressure decreases rapidly whereas diastolic blood pressure shows a delayed fall following initiation of low-dose propranolol therapy, despite the same degree of beta-adrenoceptor blockade.