Which medication is a known direct renin inhibitor?

Aliskiren is a direct renin inhibitor that works by specifically targeting the enzyme renin, which plays a critical role in the regulation of blood pressure by modulating the renin-angiotensin-aldosterone system (RAAS). By inhibiting renin, Aliskiren reduces the conversion of angiotensinogen to angiotensin I, ultimately leading to lower levels of angiotensin II, a potent vasoconstrictor. This results in vasodilation, decreased blood volume, and a reduction in blood pressure.

In contrast, Lisinopril and Losartan are drugs that target different points within the RAAS; Lisinopril is an ACE inhibitor that prevents the conversion of angiotensin I to angiotensin II, while Losartan is an angiotensin II receptor blocker (ARB) that prevents angiotensin II from exerting its effects. Amlodipine is a calcium channel blocker that primarily affects vascular smooth muscle to induce vasodilation and lower blood pressure. Thus, Aliskiren stands out as the only medication that directly inhibits renin, making it the clear answer to this question.