Use
Dobutamine (Dobutrex) is a positive inotropic agentadministered intravenously for congestive heart failure. Itresembles DA structurally but possesses a bulky 1-(methyl)-3-(4-hydroxyphenyl)propyl group on the amino group. Itpossesses a center of asymmetry, and both enantiomericforms are present in the racemic mixture used clinically. The(-) isomer of dobutamine is a potent 1-agonist, which iscapable of causing marked pressor responses. In contrast,(+)-dobutamine is a potent 1-antagonist, which canblock the effects of (-)-dobutamine. Importantly, the effectsof these two isomers are mediated via 1-receptors.Both isomers appear to be full agonists, but the (+) isomeris a more potent β1-agonist than the (-) isomer (approximatelytenfold).Dobutamine contains a catechol group and is orally inactiveand thus is given by intravenous infusion. Solutionsof the drug can exhibit a slight pink color because of oxidationof the catechol function. It has a plasma half-life ofabout 2 minutes because it is metabolized by COMT and byconjugation, although not by MAO.