Medication Class of Irbesartan
Irbesartan is an angiotensin II receptor blocker (ARB), specifically an angiotensin II type 1 (AT1) receptor antagonist. 1
Mechanism of Action
Irbesartan functions by selectively and competitively blocking the AT1 receptor subtype, which mediates the cardiovascular effects of angiotensin II. 1 The drug exhibits remarkable selectivity, with more than 8,500-fold greater affinity for AT1 receptors compared to AT2 receptors, and possesses no agonist activity. 1
Key Pharmacological Effects
Blocks vasoconstriction: Irbesartan prevents angiotensin II from binding to AT1 receptors in vascular smooth muscle, thereby inhibiting the potent vasoconstrictive effects. 1
Reduces aldosterone secretion: By blocking AT1 receptors in the adrenal gland, irbesartan decreases aldosterone release, which contributes to blood pressure reduction. 1
Does not inhibit ACE: Unlike ACE inhibitors, irbesartan does not affect angiotensin-converting enzyme, renin, or other hormone receptors and ion channels involved in cardiovascular regulation. 1
Removes negative feedback: Blockade of AT1 receptors eliminates the negative feedback of angiotensin II on renin secretion, resulting in 1.5- to 2-fold increases in plasma angiotensin II and 2- to 3-fold increases in plasma renin levels, though these do not overcome the drug's blood pressure-lowering effects. 1
Clinical Classification Context
The KDIGO guidelines consistently classify irbesartan alongside other ARBs (such as losartan and telmisartan) as part of the renin-angiotensin system (RAS) blockade class, distinguishing them from ACE inhibitors while recognizing both as effective RAS-blocking agents. 2
Important Clinical Distinction
ARBs like irbesartan should never be combined with ACE inhibitors or other ARBs, as dual RAS blockade increases risks of hyperkalemia, hypotension, and renal dysfunction without providing additional therapeutic benefit. 3, 4