Dose-response relationship in normal subjects of prenalterol, a beta-adrenergic agonist with positive inotropic and resistance lowering effects.

The acute haemodynamic effects of increasing doses of parenterally administered prenalterol-a beta-adrenergic stimulating drug-were assessed in normal subjects by means of radionuclide ventriculography. Prenalterol induced dose-related increases in the left ventricular ejection fraction and the systolic pressure end-systolic volume ratio. Left ventricular end-systolic and end-diastolic volumes decreased to the same extent accounting for an unchanged stroke volume. Cardiac output increased due to a rise in the heart rate. Systolic blood pressure increased, whereas diastolic and mean blood pressure remained unchanged. Calculated total peripheral resistance decreased significantly. The maximum effect of prenalterol on cardiac performance occurred with a dose of 18 to 36 micrograms/kg. Plasma concentrations of prenalterol showed large interindividual variations. In conclusion, prenalterol improves the pump function of the normal heart and causes a fall in peripheral vascular resistance, implying a reduction of the load on the heart. These effects may prove beneficial in the treatment of acute heart failure.