Angiotensin II receptor blockers (ARBs) or Angiotensin receptor antagornists

Losartan Candesartan

Valsartan Irbesartan

Angiotensin II has two types of receptors AT1 and AT2. Most of the effects of angiotensin II are mediated by AT1 receptors. They are vasoconstriction, aldosterone secretion and the release of noradrenaline from sympathetic nerve endings. The role of AT2 receptors is not known. ARBs competitively inhibit the binding of angiotensin II to AT1 receptor subtype. ARB’s produce effects similar to those of ACE inhibitors. The efficacy and tolerability are also similar to ACE inhibitors. Losartan is less potent than ACE inhibitors, whereas other ARBs, candesartan, valsartan and irbesartan are equipotent to ACE inhibitors. ARBs do not affect bradykinin production.

Side effects:

ARBs are better tolerated compared to ACE inhibitors. They cause headache, hypotension, weakness, rashes, nausea, vomiting and teratogenic effects. They may cause hyperkalemia in patients with renal failure or in patients on K+ sparing diuretics. They are much less likely to produce cough or angioedema. ARBs are used in hypertension, CCF & diabetic nephropathy. The efficacy and tolerability of ARBs are similar to those of ACE inhibitors. ARBs are mainly indicated in patients who develop cough with ACE inhibitors. ARBs also reduce the progression of nephropathy in patients with diabetes.

Category: Pharmacology Notes