Angiotensin II Receptor Blockers (ARBs): Step 1 Guide
Angiotensin II receptor blockers (the "-sartans") block the AT1 receptor, so angiotensin II cannot act no matter how it was produced. They share almost every benefit and risk of ACE inhibitors β blood pressure lowering, renal protection, hyperkalemia, fetal toxicity β with one key difference: they do not raise bradykinin. Step 1 tests that difference and the lab changes it produces.
Evidence-based Β· For exam prep, not medical advice
update Updated October 2026
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Written for USMLE Step 1 Β· Free to read
bolt The 60-second version
Angiotensin II receptor blockers (the "-sartans") block the AT1 receptor, so angiotensin II cannot act no matter how it was produced. They share almost every benefit and risk of ACE inhibitors β blood pressure lowering, renal protection, hyperkalemia, fetal toxicity β with one key difference: they do not raise bradykinin.
check_circleARBs (losartan, valsartan, candesartan, irbesartan) competitively block the AT1 receptor.
check_circleRenin and angiotensin II both rise; angiotensin II is high but cannot act at AT1 receptors.
check_circleNo effect on bradykinin, so cough is rare and angioedema much less common than with ACE inhibitors.
check_circleIndications mirror ACE inhibitors: hypertension, HFrEF, diabetic and proteinuric CKD; sacubitril-valsartan for HFrEF.
check_circleContraindicated in pregnancy and bilateral renal artery stenosis; do not combine with ACE inhibitors.
target What you'll be able to do Β· aligned to USMLE Step 1 Β· Pharmacology β Cardiovascular & Renal
PHARMDescribe the mechanism of AT1 receptor blockade by ARBs.
PHARMContrast ARBs and ACE inhibitors in hormone levels, bradykinin effects, and adverse effects.
PHARMList the indications for ARBs, including sacubitril-valsartan in heart failure.
PHARMRecognize the contraindications and monitoring requirements of ARBs.
How ARBs are tested on Step 1
The classic question replaces an ACE inhibitor that caused cough with an ARB, or asks how angiotensin II and bradykinin levels differ between the two classes.
workspace_premium The distinguishing lab
With an ACE inhibitor, angiotensin II falls. With an ARB, angiotensin II rises β the receptor is blocked, so feedback is lost and renin climbs, but the hormone has nowhere to act.
Mechanism
Angiotensin II acts at AT1 receptors to cause vasoconstriction, aldosterone and ADH release, thirst, and cardiac and vascular remodeling. ARBs block that receptor directly.
ARBs act at the receptor. Because angiotensin II can also be made by non-ACE enzymes such as chymase, receptor blockade is a more complete block of angiotensin II action.
ARBs vs ACE inhibitors
Choose between the classes mainly by tolerability; their outcome benefits are similar.
Same benefits, different side effects. Combining an ACE inhibitor with an ARB increases hyperkalemia and kidney injury without improving outcomes.
Variable
ACE inhibitor
ARB
Renin
β
β
Angiotensin I
β
β
Angiotensin II
β
β
Aldosterone
β
β
Bradykinin
β
No change
Serum KβΊ
β
β
Aliskiren, a direct renin inhibitor, lowers renin activity, angiotensin I, and angiotensin II.
Indications and special agents
ARBs are used wherever ACE inhibitors are, and are the usual substitute when ACE inhibitors cause cough.
Use
Note
Hypertension
First-line option; especially with diabetes or CKD
HFrEF
Sacubitril-valsartan (ARNI) reduces mortality more than enalapril
Diabetic nephropathy, proteinuric CKD
Losartan and irbesartan slow progression
Marfan syndrome
Losartan may slow aortic root dilation (TGF-Ξ² effect)
Gout with hypertension
Losartan has a mild uricosuric effect
Sacubitril inhibits neprilysin, which raises natriuretic peptides β and bradykinin, so ARNI must not be given within 36 hours of an ACE inhibitor (angioedema risk).
Adverse effects and contraindications
ARBs share the hemodynamic and fetal risks of ACE inhibitors.
ARB adverse effects. Monitor potassium and creatinine 1β2 weeks after starting or increasing the dose.
functions Worked example β interpret the hormones
A patient with hypertension has high plasma renin activity, high angiotensin II, and low aldosterone. Serum potassium is 5.3 mEq/L. Which drug is the patient most likely taking?
High renin means angiotensin II feedback on the juxtaglomerular cells is gone.
Angiotensin II is high, so its production is intact β an ACE inhibitor would lower it.
Aldosterone is low despite high angiotensin II, so angiotensin II cannot act on its receptor.
High potassium follows from low aldosterone.
Answer. An angiotensin II receptor blocker such as losartan.
Rarely. ARBs do not inhibit ACE, so bradykinin does not accumulate. They are the standard replacement when an ACE inhibitor causes cough.
Can you give an ARB after ACE-inhibitor angioedema?expand_more
Cautiously. ARBs carry a much lower angioedema risk, and many patients tolerate them, but a small cross-reaction risk exists, so they are used with careful monitoring.
Why is angiotensin II high with an ARB?expand_more
Blocking the AT1 receptor removes angiotensin II feedback on renin release, so renin and angiotensin II rise, but the angiotensin II cannot act on the blocked receptor.
Should an ACE inhibitor and an ARB be combined?expand_more
No. Dual blockade raises the risk of hyperkalemia, hypotension, and acute kidney injury without improving outcomes.
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