Inotropic drugs and their mechanisms of action
H Scholz
This report describes various old and new positive inotropic drugs with respect to their mechanisms of action. Drugs with established cardiotonic effects include cardiac glycosides, beta 1-adrenergic agents, glucagon, histamine and the methylxanthines. New agents discussed are prenalterol, beta 2- and alpha-adrenergic drugs, amrinone and sulmazole. Prenalterol is a beta 1-adrenergic agent. Beta 2-adrenergic drugs, amrinone and sulmazole, combine a positive inotropic and a vasodilator effect. The latter resemble theophylline and other methylxanthines in that they appear to act mainly as phosphodiesterase inhibitors with a subsequent increase in cyclic adenosine monophosphate (cAMP). The mechanism of the positive inotropic effect of alpha-adrenergic stimulating agents (for example, phenylephrine) is unknown. It is independent of the cAMP system and is not accompanied by changes in frequency.
