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Angiotensin-Converting Enzyme Inhibitors (ACEIs), Angiotensin II Receptor Antagonists (ARBs), or Direct Renin Inhibitors (DRI) for Adults With Hypertension

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Background: Pharmacological Blockade of the Renin-Angiotensin System

Among the many choices in antihypertensive therapy, some of the most common are those aimed at affecting the renin-angiotensin-aldosterone (renin) system. The renin system is an important mediator of blood volume, arterial pressure, and cardiac and vascular function. Components of this system can be identified in many tissues, but the primary site of renin release is the kidney. The renin system can be triggered by sympathetic stimulation, renal artery hypotension, and decreased sodium delivery to  the distal tubule. Through proteolytic cleavage, renin acts on the oligopeptide substrate angiotensinogen to produce the decapeptide angiotensin I. In turn, two terminal peptide residues of angiotensin I are removed by the angiotensin converting enzyme (ACE) to form the octapeptide angiotensin II. Angiotensin II acts directly on the resistance vessels to: increase systemic vascular resistance and arterial pressure; stimulate the adrenal cortex to release aldosterone, which leads to increased sodium and  water reabsorption and potassium excretion; promote secretion of antidiuretic hormone, which leads to fluid retention; stimulate thirst; promote adrenergic function; and increase cardiac and vascular hypertrophy. Pharmacological agents that are approved for use in adults with hypertension and act directly on the renin system include ACEIs, ARBs, and a DRI called aliskiren.