Relationship of plasma catecholamines to blood pressure in hypertensive patients during beta-adrenoceptor blockade with and without intrinsic sympathomimetic activity

Abstract

1 This study was designed to follow changes in plasma catecholamine concentrations during β-adrenoceptor blockade using doses of antagonists which decreased the mean arterial pressure (MAP) by about 15 mm Hg. Noradrenaline, adrenaline and dopamine were radioenzymatically determined in 34 patients with moderate essential hypertension during an 8 week course of treatment with either pindolol (with intrinsic sympathomimetic activity, ISA) or propranolol (without ISA). Plasma catecholamines were determined before and 1, 7, 28 and 56 days after commencement of treatment and 1 week after discontinuation of treatment.

2 After one day of pindolol therapy plasma catecholamine concentrations were decreased, but no decrease in MAP was observed. After one day of propranolol therapy, however, MAP was decreased, but except for increased levels of adrenaline, plasma catecholamines showed no changes.

3 On the 56th day of therapy both β-adrenoceptor blockers had decreased the MAP. Pindolol therapy had caused a decrease in all three catecholamines whereas propranolol had caused no change except for decreased dopamine levels.

4 One week after cessation of propranolol therapy catecholamines were decreased but the MAP had begun to return to initial values; after cessation of pindolol therapy however, the MAP remained decreased.

5 The dissimilar relationships between blood pressure and catecholamine concentration during pindolol and propranolol therapy are evidence for multiple and different modes of action for β-adrenoceptor blockers with and without ISA. This study demonstrates that catecholamine concentrations were generally decreased during low-dose β-adrenoceptor blocker therapy, with lower catecholamine levels during pindolol treatment than during propranolol treatment.