Cardiovascular effects of prenalterol (H133/22) in normal man

1 Prenalterol, (S‐(‐)‐1‐(4 hydroxyphenoxy)‐3‐isopropylaminopropanol‐2 hydrochloride) a cardio‐selective beta‐adrenergic receptor agonist, was infused intravenously into six normal male volunteers to determine the cardiovascular effects of this drug. 2 On different occasions, each volunteer received a placebo infusion, an infusion of 0.5 mg prenalterol and an infusion of 1 mg prenalterol. Cardiac output (impedance cardiography), arterial pressure (sphygmomanometry), heart rate and ECG were measured throughout. 3 Prenalterol produced a statistically significant increase in cardiac output and at the end of the infusion this increase was 24% with 0.5 mg and 29% with 1 mg, mainly due to an increase in stroke volume (18% and 17%) with a lesser change in heart rate (+2 and +7 beats/min). Pulse pressure increased but mean arterial pressure showed little change. Peripheral resistance fell by 18% and 20%. As indicated by systolic time indices myocardial contractility increased. 4 Prenalterol at plasma concentrations in excess of 20 nmol l‐1 produced significant inotropic effects but did not markedly increase heart rate at concentrations of 60 nmol l‐1.