Which of the following medications is classified as an Angiotensin Receptor Blocker (ARB)?

Losartan is classified as an Angiotensin Receptor Blocker (ARB), making it the correct choice in this context. ARBs work by blocking the effects of angiotensin II, a hormone that can constrict blood vessels and increase blood pressure. This mechanism helps to lower blood pressure and provides renal protection, particularly in patients with diabetes or heart failure.

In contrast, the other medications listed serve different purposes. Metoprolol is a beta-blocker that primarily affects heart rate and myocardial contractility. Triamterene is a potassium-sparing diuretic that helps manage fluid retention but does not impact the angiotensin system. Diltiazem is a calcium channel blocker, which primarily affects myocardial contractility and vascular smooth muscle, leading to vasodilation. Each of these medications has distinct pharmacological effects and indications, further highlighting why Losartan is uniquely identified as an ARB.