Experimental pharmacology indicates that
prenalterol is a selective beta 1-adrenoceptor activator. In 5 normal individuals, 15 minutes after the
drug (infused at a dose of 15 micrograms/kg over 5 min) the following circulatory changes were seen: a) increase of cardiac index (+31%), heart rate,
stroke index, systolic aortic pressure, left and right ventricular mean rate of ejection and mean rate of the pressure rise in either ventricle during the pre-ejection phase; b) reduction of systemic vascular resistance (-18%), appearance, built-up and disappearance times in the left ventricular
dye dilution curves. Pulmonary systolic, diastolic and wedge pressures and vascular resistance did not vary consistently. The circulatory effects persisted almost unchanged 30 minutes after the infusion. In a group of 5 patients with
heart failure due to primary
congestive cardiomyopathy, refractory to conventional
therapy, the haemodynamic response to
prenalterol (infused at a dose of 30 micrograms/kg over 5 min) was qualitatively similar to that of normal subjects in 3 cases. In 2 other patients cardiac performance deteriorated. The reasons for this paradoxical effect were not identified. These preliminary results suggest that
prenalterol is a potent selective inotropic agent in man, that may assist in the therapeutic management of refractory
heart failure due to
congestive cardiomyopathy. However, careful haemodynamic monitoring is advisable for its use in this dysfunction until broader clinical experience can be accumulated.