Influence of propranolol and pindolol on the haemodynamic effects of papaverine, isoprenaline and noradrenaline in hypertensive patients

The influence of two beta-adrenoceptor antagonists, propranolol and pindolol, on the haemodynamic effects of papaverine, isoprenaline and noradrenaline was investigated in 9 male patients with first degree essential hypertension. Propranolol and pindolol were given according to a doubleblind, crossover scheme. Heart rate and blood pressure were measured before and after each treatment. Propranolol 670 microgram/kg i.v. reduced the supine and standing systolic blood pressures by 2.3% and 1.6%, respectively. Similarly, the intravenous administration of pindolol 35 microgram/kg reduced supine and standing systolic blood pressure by 5.5% and 8.3% respectively (clinically insignificant). Neither drug affected diastolic blood pressure. Following propranolol, there were moderate reduction in supine and standing heart rates, respectively by 24% and 20% (p < 0.001). Similarly, but to a lesser extent, pindolol reduced supine and standing heart rate by 12% and 17% (p < 0.001). The effects of papaverine, which, at 1.5 mg/kg i.v. reduced systolic blood pressure by 5-10% and increased heart rate by 8-15%, were not significantly influenced by the beta-blockers. The blood pressure and heart rate responses to isoprenaline, on the other hand, were attenuated or inhibited by both beta-blockers. While the beta-blockers inhibited the beta-adrenoceptor component of noradrenaline, the pressor component of noradrenaline, which is mediated through the alpha-adrenoceptors, was not influenced by propranolol, but was inhibited after pindolol. It is concluded that pindolol differs qualitatively from propranolol in that it inhibited both the alpha and beta-adrenoceptor effects of noradrenaline.