• Dopamine and dobutamine are used for short-term inotropic support of the failing heart.

• Dobutamine is less arrhythmogenic and produces less tachycardia compared to endogenous catecholamines or isoproterenol.

Dobutamine:

• Dobutamine is a racemate that binds to and activates beta-1 and beta-2 adrenoceptor subtypes. The (-) enantiomer stimulates alpha 1 and alpha 2 receptors, but this effect in humans appear negated by binding of the inactive (+) enantiomer. Therefore the positive inotropic action mediated by beta receptor activation predominates.

• Dobutamine does not activate dopamine receptors and therefore does not increase renal blood flow.

• Because of its vasodilator properties, dobutamine's positive inotropism is accompanied by a decrease in afterload. For this reason dobutamine is favored over dopamine for most advanced heart failure patients who have not improved with digoxin, diuretics, and vasodilator therapy.

Dopamine

• Dopamine has limited utility in patents with left ventricular dysfunction. It often produces tachycardia which may increase left ventricular work.

• Dopamine-induced vasodilation is mediated by direct stimulation of D1 and D2 post-synaptic dopamine receptors. Vasodilation of renal vasculature is noteworthy and may benefit patients with marginal GFR due to poor renal perfusion.