Which of the following is a calcium channel blocker?

• A. Amlodipine
• B. Metoprolol
• C. Enalapril
• D. Losartan

Answer: (D)

Calcium channel blockers work by blocking L-type calcium channels in vascular smooth muscle and heart muscle, which lowers intracellular calcium and leads to relaxation of smooth muscle and vasodilation, reducing blood pressure. Among the options, the medication that fits this class is amlodipine, a dihydropyridine calcium channel blocker that mainly relaxes vascular smooth muscle to lower blood pressure and help with angina. The other drugs belong to different classes: metoprolol is a beta-blocker that reduces heart rate and contractility; enalapril is an ACE inhibitor that decreases angiotensin II formation; losartan is an angiotensin II receptor blocker that blocks the receptor.