Studies on the effects of propranolol on plasma catecholamine levels in patients with essential hypertension

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Abstract
The influence of the .beta.-receptor blocking agent propranolol on plasma catecholamine concentrations was studied in 8 patients with essential hypertension. The study was of single blind crossover design. Propranolol given in oral doses ranging from 60-240 mg daily for a period of 3 wk decreased blood pressure and heart rate. The .beta.-adrenergic blocking agent caused plasma catecholamine levels to increase both at rest and during bicycle exercise. Chromatographical analysis showed that concentrations of noradrenaline [norepinephrine] and of adrenaline [epinephrine] rose during treatment with propranolol. Dopamine-.beta.-hydroxylase activity in plasma was not altered. The urinary excretion of noradrenaline, adrenaline and 4-hydroxy-3-methoxy mandelic acid did not change during .beta.-receptor blockade. Antihypertensive doses of propranolol by decreasing cardiac output may cause an activation of the sympathoadrenal system.