Influence of metoprolol* and propranolol on hemodynamic effects induced by adrenaline and physical work

Abstract:The influence of intravenously administered metoprolol (10 mg), propranolol (5 and 10 mg) and saline on hemodynamic effects induced by adrenaline and physical work were studied in healthy volunteers. In the doses used the two β‐blockers were approximately equipotent in reducing the heart rate and systolic blood pressure during exercise. Adrenaline induced an increase of the heart rate, systolic blood pressure and forearm blood flow, while the mean blood pressure, diastolic blood pressure and vascular resistance in the forearm decreased. The two β‐blockers interacted differently with adrenaline. When adrenaline was infused after propranolol the mean and diastolic blood pressure increased as did also vascular resistance in the forearm. Adrenaline now had no significant effect on the forearm blood flow, while the heart rate decreased. After metoprolol, adrenaline still induced a decrease of the diastolic blood pressure and an increase of the forearm blood flow, but the effect of adrenaline on these variables seemed to be inhibited to a great extent. The decrease of the mean blood pressure after adrenaline was blocked by metoprolol, while the effect on the vascular resistance in the forearm and the heart rate was not significantly changed. The difference in interaction of the two β‐blockers with adrenaline is interpreted as being caused by a much less pronounced effect of metoprolol on the adrenergic vascular β2‐receptors compared to propranolol in the doses studied.