Effects of prenalterol, a partial beta adrenoceptor agonist, on the left ventricular function in anesthetized cardiac denervated beagle dogs

Cardiovascular effects of prenalterol, a partial beta adrenoceptor agonist, were investigated in pentobartial anesthetized dogs. In these preparations, in which the heart was acutely denervated, intravenous administration of prenalterol significantly enhanced contractility (left ventricular max dP/dt) as well as heart rate, and reduced left atrial pressure. Hence the data confirmed that this agent is an effective inotropic as well as a chronotropic agent. Ventricular function curves were determined in these studies to establish the efficacy of the myocardium in handling volume loads at various filling pressures. In order to relate the increased output directly to increases in inotropy, heart rate was kept constant by electrical pacing. Prenalterol significantly shifted these curves upward and to the left, indicating enhanced contractility. In a separate series, it was demonstrated that the inotropic effect of prenalterol persists for longer durations as indicated by the significant shift that occurred in left ventricular function curves 70 min after administration of a single dose of the drug. The data collectively suggest that prenalterol, an orally effective inotropic agent, possesses prolonged duration of action; hence, this drug may be more preferable than dopamine or dobutamine in the treatment of heart failure since the effects of these two agents are transient and are subjected to tolerance during continuous intravenous infusions.