Some new positive inotropic agents

Abstract

In the search for new effective positive inotropic agents for the treatment of congestive heart failure (CHF), interest has focused mainly on two groups of agents namely adrenoceptor agonists and drugs inhibiting phosphodiesterase. Common for drugs belonging to both groups is that their positive inotropic effects seem to involve an increase in the intracellular concentration of cyclic AMP. Drugs acting by stimulation of beta 1- and/or beta 2-adrenoceptors (e.g. dopamine, dobutamine, prenalterol, pirbuterol, salbutamol, terbutaline, fenoterol) have initial beneficial effects, but seem to be ineffective for long-term treatment. This has been suggested to be due to desensitization of the beta-adrenoceptors, and means, if this effect can be definitely established, that beta-adrenoceptor stimulation should be restricted to the acute treatment of CHF. Among drugs inhibiting phosphodiesterase, sulmazole, amrinone, milrinone, and fenoximone all have been shown to improve cardiac performance in patients with CHF during short-term treatment. However, results of long-term treatment with most of these drugs seem less encouraging. It has been suggested that these drugs may not be an effective approach to treatment of patients with CHF, since even if it is possible to achieve short-term gains, the long-term effects on the myocardium may be detrimental. Their ultimate place in the treatment of CHF remains to be established.