Newer inotropic agents.

Impairment of myocardial contractility results in reduction of cardiac output and activation of various compensatory mechanisms which eventually work to disadvantage. Drug treatment is directed towards improving myocardial contractility with inotropic agents and relieving congestion and vasoconstriction with diuretics and vasodilators. Digitalis is a relatively modest inotropic agent with considerable toxic potential and there is a need for alternative inotropic agents which are potent, active orally, effective long term and have minimal adverse effects. A number of beta agonists have been evaluated but their application appears limited to some extent by the development of tolerance, probably due to downregulation of myocardial beta receptors. Of the non-adrenergic inotropic agents currently under evaluation, amrinone appears most promising although its mechanism of action is not known.