USMLE

Angiotensin II Receptor Blockers (ARBs)

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Renal Pharm
  1. ACE Inhibitors
  2. Aldosterone Receptor Blockers (Spironolactone, Eplerenone)
  3. Ethacrynic Acid
  4. Loop Diuretics (Furosemide, Bumetanide, Torsemide)
  5. Mannitol
  6. Acetazolamide
  7. ENaC Blockers (Amiloride, Triamterene)
  8. Thiazide Diuretics
  9. Angiotensin II Receptor Blockers (ARBs)

Summary

Angiotensin receptor blockers, or ARBs for short, are a class of drugs that have a common “-sartan” ending. These drug names include losartan, candesartan, and valsartan.  As their name suggests, these drugs work by blocking angiotensin II receptors.  This reduces angiotensin-mediated vasoconstriction and suppresses aldosterone release - both factors that contribute to lowering of blood pressure.

ARBs have very similar clinical uses to ACE inhibitors. Clinically, ARBs are used in the treatment of high blood pressure, although they are a second-choice drug, used in patients who cannot tolerate ACE inhibitors. By reducing blood pressure and afterload, ARBs are also helpful in the treatment of heart failure. Finally, ARBs can help protect the kidneys from damage in patients with diabetes or hypertension. In general, ARBs are prescribed to patients who are intolerant to ACE inhibitors, providing similar vascular benefits without the same side effect profile.

However, ARBs do have some of their own side effects. For example, high doses of these drugs can lead to hypotension. They can also induce hyperkalemia by decreasing aldosterone release. ARBs are also teratogenic and should be avoided in pregnant women. Lastly, ARBs are contraindicated in people with bilateral renal artery stenosis, as their use can lead to rapid kidney failure.

Key Points

  • Angiotensin II Receptor Blockers (ARBs)
    • Drug Names (-sartan endings)
      • Losartan
      • Candesartan
      • Valsartan
    • Mechanism
      • Angiotensin II receptor blocker
        • Technically blocks the angiotensin II type 1 receptor
        • May cause a compensatory increase in renin (plasma renin activity = PRA)
    • Clinical Use
      • Intolerance to ACE inhibitors
        • Cough
          • Replacing a patient's ACE inhibitor with an ARB will eliminate the cough while still providing the same long-term renovascular benefits.
        • Angioedema
      • Otherwise, prescribed for the same indications as an ACE inhibitor:
        • Systolic heart failure
          • Provides a mortality benefit, along with beta blockers, and aldosterone antagonists (spironolactone and eplerenone)
          • May slow adverse remodeling of heart
        • Hypertension
          • ACEIs are still first-line, since ACEIs are proven to reduce mortality while ARBs do not [AAFP]
          • Used in hypertension and heart failure due to left ventricular systolic dysfunction
        • Diabetic nephropathy
          • Decreases rate of glomerular basement membrane thickening, prevents progression to chronic kidney disease
    • Adverse Effects
      • Hypotension
        • This is a obvious side effect seen with all antihypertensive agents
      • Hyperkalemia
        • ARBs decrease downstream aldosterone production, which reduces potassium excretion by the kidneys
      • Teratogenic
        • ARBs are teratogens that cause fetal kidney malformations
      • Contraindicated in bilateral renal artery stenosis
        • In bilateral renal artery stenosis, angiotensin II is necessary to maintain GFR. Inhibiting angiotensin II’s effects can lead to rapid renal failure.
        • Look for a large rise in creatinine after starting an ACE inhibitor
      • Mildly increase creatinine by reducing GFR
      • Elevates risk for lithium toxicity