Acute hemodynamic effects and cardioselectivity of acebutolol, practolol, and propranolol

Abstract

The relative cardioselectivity of acebutolol in man was studied by comparing its hemodynamic effects with those of two other β‐blockers—propranolol, a nonselective β‐blocker, and practolol, a cardioselective β‐blocker. Hemodynamic studies (Cardio‐Green) were performed on hypertensive patients before and after intravenous administration of acebutolol 1 mg/kg (9 patients), practolol 50 mg (8 patients), and propranolol 10 mg (21 patients). The hemodynamic changes after acebutolol were similar to those obtained with practolol but not as striking as those with propranolol. Acebutolol did not differ significantly from practolol with respect to effects on heart rate (HR), mean arterial pressure, cardiac output, and total peripheral resistance (TPR). Propranolol led to a greater reduction in HR (p < 0.001) and a larger increase in TPR (p < 0.025) than acebutolol; there was no significant difference between the 2 in their effects, on arterial pressure and cardiac output. The relative cardioselectivity of these 3 drugs was further investigated by comparing the degree of blockade of chronotropic and diastolic blood pressure (DPB) responses to isoproterenol (0.03 µg/kg/min). In terms of cardiac β‐blockade, acebutolol was more effective than practolol and approximately equipotent to propranolol in blocking the chronotropic response to isoproterenol; it induced significantly less blockade of the DBP decrease with isoproterenol than propranolol but more than practolol. The data suggest that acebutolol induces a greater effect on cardiac β‐receptors (β1) than on arteriolar receptors (β2) and is relatively more cardioselective than propranolol but less so than practolol.