Which medication is an example of a calcium channel blocker?

Diltiazem is a medication that belongs to the class of calcium channel blockers, which work by inhibiting the influx of calcium ions into cardiac and smooth muscle cells. This action facilitates the relaxation of vascular smooth muscles, leading to decreased peripheral vascular resistance and lower blood pressure. In addition to its antihypertensive effects, diltiazem is also used to manage angina and certain arrhythmias due to its ability to slow down the conduction through the heart's electrical conduction system.

The other medications listed are from different classes: Atenolol and Metoprolol are beta-blockers, which primarily work by blocking the effects of adrenaline on beta receptors, reducing heart rate and myocardial contractility. Lisinopril is an ACE inhibitor that works by inhibiting the conversion of angiotensin I to angiotensin II, leading to vasodilation and reduced blood pressure. Hence, diltiazem stands out as the representative calcium channel blocker among the options provided.