Which of the following is NOT considered a common inotropic medication?

Diltiazem is not considered a common inotropic medication because it primarily functions as a calcium channel blocker. Its main use is to manage hypertension and control heart rate in certain arrhythmias, rather than to enhance myocardial contractility.

On the other hand, Milrinone, Dopamine, and Dobutamine are recognized for their inotropic properties, which means they are used to increase the strength of heart contractions. Milrinone is a phosphodiesterase inhibitor that improves cardiac output and decreases vascular resistance, making it effective in treating heart failure. Dopamine, depending on the dosage, can increase heart rate and contractility, particularly at moderate to high doses. Dobutamine is a well-known positive inotrope that enhances cardiac contractility, widely used in patients with heart failure.

Therefore, while many cardiovascular medications exist, Diltiazem is distinguished by its different mechanism and primary uses, disqualifying it from being classified as an inotropic agent.