Effects of oxprenolol and propranolol on systolic time intervals

Twenty patients with coronary heart disease participated in a double-blind, randomized, crossover study on three study mornings to evaluate the effect of oral oxprenolol 80 mg, oral propranolol 80 mg, and placebo on left ventricular contractility. Systolic time intervals were performed in the control period and at 60, 90, 120, 150, 180, 240, 300, and 360 min after medication. None of 20 patients developed adverse effects. The 80-mg doses of oxprenolol and propranolol had a negative chronotropic effect, with the resting heart rate slightly but consistently decreased more after propranolol, attaining statistical significance at 90, 150, and 300 min. That the 80-mg doses of oral oxprenolol and propranolol also induced a negative inotropic effect was indicated by a similar prolongation of the external isovolumic contraction time and pre-ejection period intervals. This equipotent dose of oxprenolol in producing a negative inotropic effect induces less resting bradycardia than propranolol.