Which of the following medications is NOT a calcium channel blocker?

Lasix is recognized as a diuretic, specifically a loop diuretic, which operates by inhibiting sodium and chloride reabsorption in the kidneys. Its primary role is to help reduce fluid retention and manage blood pressure. Unlike calcium channel blockers, which primarily function by inhibiting calcium ions from entering cells of the heart and blood vessel walls, Lasix does not have any calcium channel blocking properties.

In contrast, Norvasc, Cardizem, and Verapamil are all classified as calcium channel blockers. Norvasc, or amlodipine, works by relaxing the blood vessels to improve blood flow, while Cardizem, or diltiazem, and Verapamil also lower blood pressure through similar mechanisms by affecting the heart's rate and its contractility alongside vasodilation. Thus, recognizing Lasix as a diuretic rather than a calcium channel blocker clarifies why it is the correct choice for this question.