Which antihypertensive agent is a direct renin inhibitor?

Aliskiren is a direct renin inhibitor, which means it specifically targets the enzyme renin involved in the renin-angiotensin-aldosterone system (RAAS). By inhibiting renin, Aliskiren decreases the conversion of angiotensinogen to angiotensin I, ultimately leading to lower levels of angiotensin II, a potent vasoconstrictor. This action results in vasodilation, decreased blood pressure, and reduced aldosterone secretion, contributing to reduced fluid retention.

Other choices do not fit the classification of direct renin inhibitors. Losartan is an angiotensin II receptor blocker (ARB) that prevents the effects of angiotensin II, while Atenolol is a beta-blocker that decreases heart rate and cardiac output. Hydrochlorothiazide is a thiazide diuretic that lowers blood pressure by promoting the excretion of sodium and water. Therefore, Aliskiren is unique in its direct action on renin, distinguishing it from these other antihypertensive agents.