Which of the following medications is both a vasoconstrictor and an agent that increases the strength of cardiac contraction?

Dobutamine (Dobutrex) is recognized for its dual role as both a vasoconstrictor and an agent that enhances the strength of cardiac contraction (inotropic effect). It primarily acts on beta-1 adrenergic receptors in the heart, leading to increased myocardial contractility. This makes it particularly useful in treating conditions such as heart failure, where improving the heart's pumping ability is crucial.

Moreover, while dobutamine does have some vasodilatory effects at low doses due to its action on beta-2 receptors, its primary pharmacological action is to increase cardiac contractility. In clinical scenarios, especially in acute heart failure, dobutamine is often administered to help improve cardiac output.

Given its specific effects on heart function, dobutamine is correctly identified as the medication that satisfies both criteria in the question.