Antihypertensive and hormonal responses to beta-blockade with intrinsic sympathomimetic activity: pindolol versus epanolol.

After a 2-week placebo period, 30 men, aged 60 years (mean), with mild or moderate hypertension were randomly assigned to one of three treatment groups: pindolol, 10 mg b.i.d.; epanolol, 200 mg b.i.d.; and epanolol, 400 mg q.d. At the end of the placebo period and of 4 weeks of active treatment, heart rate, blood pressure, plasma renin activity (PRA), and nonepinephrine (NE) concentration of subgroups of subjects, were measured during isoproterenol infusion (30 ng/kg.min-1 for 15 min) and submaximal ergometric exercise (89 W, mean). Sitting heart rates were reduced with 200 mg b.i.d. epanolol (p less than 0.01) but unchanged with pindolol and 400 mg q.d. epanolol. Reductions of systolic and diastolic blood pressures occurred in all treatment groups but were most pronounced with pindolol. Isoproterenol-induced cardioacceleration and rise in PRA and plasma NE concentration were abolished by pindolol but only attenuated by epanolol. Pindolol also abolished the isoproterenol-induced reduction in diastolic blood pressure; epanolol had no effect on it. The hemodynamic and hormonal responses to exercise were attenuated by pindolol and epanolol in proportion to their beta-blocking activities. In the doses used, epanolol had moderate beta 1-selective blocking action. The intrinsic sympathomimetic activity of epanolol is dose dependent.