Renin inhibitors produce vasodilation by inhibiting the activity of renin, which is responsible for stimulating angiotensin II formation. Renin is a proteolytic enzyme that is released by the kidneys in response to sympathetic activation, hypotension, and decreased sodium delivery to the distal renal tubule. Once released into the circulation, renin acts on circulating angiotensinogen to form angiotensin I. Angiotensin I is then converted to angiotensin II by angiotensin converting enzyme. Angiotensin II has a several important actions including vasoconstriction, stimulation of aldosterone, renal retention of sodium and water, enhancing sympathetic activity by increasing norepinephrine release by sympathetic nerves, and stimulating cardiac and vascular hypertrophy. Aliskiren is one of the renin inhibitors.