Irbesartan/amlodipine (Aprovasc®) is an angiotensin-receptor blocker/calcium-channel blocker fixed-dose single-pill combination, whose constituent drugs exert additive effects when coadministered. It is indicated in patients whose blood pressure is not adequately controlled on irbesartan or amlodipine monotherapy. Irbesartan and Amlodipine: The pharmacodynamic properties of each drug, Irbesartan and Amlodipine, provide an addition of antihypertensive effects when administered in combination against the effect observed with both components separately. Both the AT1 receptor blocker and the calcium channel antagonist lower blood pressure by reducing peripheral resistance, but blocking calcium flow and reducing vasoconstriction by angiotensin II are complementary mechanisms. Irbesartan: Mechanism of action: Irbesartan is a specific antagonist of angiotensin II receptors (AT1 subtype). Angiotensin II is an important component of the renin-angiotensin system, it participates in the pathophysiology of hypertension and in sodium homeostasis. Irbesartan does not require metabolic activation for its action. Irbesartan blocks the potent vasoconstriction and aldosterone secretion effects produced by angiotensin II, by selective antagonism of angiotensin II receptors (AT1 subtype) located in vascular smooth muscle cells and in the adrenal cortex. Irbesartan has no agonist activity at the AT1 receptor and has a much higher affinity (more than 8,500 times) for the AT1 receptor than for the AT2 receptor (a receptor that has not been shown to be associated with cardiovascular homeostasis). Irbesartan does not inhibit the enzymes that participate in the renin-angiotensin system, that is, the angiotensin-converting enzyme (ACE), nor does it affect other hormone receptors or ion channels that are involved in the cardiovascular regulation of blood pressure and in sodium homeostasis. AT1 receptor blockade caused by irbesartan disrupts the feedback loop within the renin-angiotensin system, resulting in increases in plasma renin and angiotensin II levels.