Interactions between diuretics and propranolol in treatment of arterial hypertension

Small doses of the beta-adrenergic blocking agent propranolol added to a regimen of diuretic treatment with chlorthalidone in outpatients with essential hypertension depressed the rise in plasma renin activity induced by chlorthalidone significantly although not entirely. Simultaneously, a reduction in blood pressure occurred beyond that already achieved by the diuretic agent. Increasing the dose of propranolol, from 40 to 160 mg/day, caused an additional antihypertensive response with no further renin depression. It is concluded that the antihypertensive effect of large doses of propranolol is due mainly to a renin-independent mechanism, but the reduction in pressure that follows addition of a small dose of the beta blocker may be due to a renin-dependent mechanism brought into action by the rise in plasma renin that is induced by concurrent diuretic therapy.