Comparative haemodynamic dose-response effects of intravenous propranolol, acebutolol and penbutolol in angina...

The relevance of the ancillary pharmacological properties of intrinsic sympathomimetic activity (ISA) and cardioselectivity to the haemodynamic profile following intravenous beta-blockade was examined in a randomised study of propranolol (16 mg), acebutolol (160 mg) or penbutolol (4 mg) in 30 patients with stable angina pectoris. Haemodynamic measurements were undertaken at rest and during four minutes steady-state supine bicycle exercise (25 to 50 W), load limited to the angina threshold, before and after each drug. The randomised groups were statistically similar for major haemodynamic and clinical variables. The plasma concentrations achieved for each drug were in the therapeutic range. At rest, propranolol resulted in greater reductions in resting cardiac output and greater increase in pulmonary artery occluded pressure compared with acebutolol and penbutolol. During the sympathetic stimulus of dynamic exercise, penbutolol resulted in less depression of exercise cardiac performance than either acebutolol or propranolol. These observations are compatible with previous studies which suggested that the possession of ISA by a beta-blocking drug offset the depression of cardiac performance following intravenous beta-blockade; the benefits of ISA on haemodynamic profile appeared maximum at rest and were reduced or abolished during dynamic exercise.