Hemodynamic and adrenergic responses of bevantolol and propranolol in hypertensives

The hemodynamic and neurohumoral responses of 21 thiazide-resistant hypertensives receiving sequential chronic therapy with propranolol and bevantolol, a new cardioselective beta-1 blocker, were studied and compared with their responses to placebo. The objective was to determine to what extent decreased circulation levels of catecholamines and renin activity contributed to the hypotensive action of bevantolol and whether it demonstrated a significant sparing effect on vascular resistance. Both propranolol and bevantolol lowered supine and erect blood pressures to a comparable extent but the response of diastolic pressure to upright posture was maintained. Resting heart rates were lowered and postural tachycardia was attenuated. Propranolol induced a greater decrease in forearm blood flow and greater increase in vascular resistance than bevantolol. Both drug therapies were associated with lowered plasma concentrations of noradrenaline and adrenaline, while the decrease in noradrenaline levels was linearly related to the fall of mean arterial pressure for both drugs. Plasma renin activity was lowered only to a marginal extent by either drug but aldosterone concentrations were significantly reduced to a comparable extent by both drugs. The results suggest that a negative chronotropic action on the heart and an overall reduction in sympathetic nervous tone both contribute to the hypotensive effects of bevantolol and propranolol, but reduction of plasma renin activity may be of lesser importance. Bevantolol demonstrated a significant vascular sparing effect in this patient group compared with propranolol.