Can olmesartan and losartan (both angiotensin‑II receptor blockers) be taken together?

Can You Take Olmesartan and Losartan Together?

No, you should not take olmesartan and losartan together—combining two ARBs (angiotensin receptor blockers) is explicitly contraindicated and potentially harmful.

Why This Combination Is Prohibited

Dual blockade of the renin-angiotensin system (RAS) with two ARBs is associated with increased risks of hypotension, hyperkalemia, and acute renal failure without providing additional cardiovascular benefit. 1

Specific Guideline Recommendations

• The 2024 ESC Guidelines explicitly state: "Combining two RAS blockers (ACE inhibitor and an ARB) is not recommended." 1 This prohibition extends to combining two ARBs as well.

• The 2017 ACC/AHA Guidelines provide a Class III (Harm) recommendation with Level A evidence: "Simultaneous use of an ACE inhibitor, ARB, and/or renin inhibitor is potentially harmful and is not recommended to treat adults with hypertension." 1

Evidence from Clinical Trials

The VA NEPHRON-D trial demonstrated the dangers of dual RAS blockade: 2

• Patients receiving combination RAS inhibitor therapy (losartan plus lisinopril) experienced increased incidence of hyperkalemia and acute kidney injury compared to monotherapy
• No additional benefit was observed for the combined endpoint of decline in GFR, end-stage renal disease, or death
• The trial was stopped early due to safety concerns

FDA Drug Label Warnings

Both olmesartan and losartan FDA labels explicitly warn against dual RAS blockade: 3, 2

• "Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of hypotension, hyperkalemia, and changes in renal function (including acute renal failure) compared to monotherapy"
• "Most patients receiving the combination of two RAS inhibitors do not obtain any additional benefit compared to monotherapy"
• "In general, avoid combined use of RAS inhibitors"

What to Do Instead

If blood pressure is not controlled on a single ARB:

1. Increase the dose of the current ARB to maximum recommended levels (olmesartan 40 mg or losartan 100 mg daily) 1

2. Add a different class of antihypertensive medication, preferably: 1

   • A dihydropyridine calcium channel blocker (e.g., amlodipine), OR
   • A thiazide/thiazide-like diuretic (e.g., chlorthalidone, hydrochlorothiazide)

3. Consider switching to a more potent ARB if inadequate response—olmesartan has demonstrated superior blood pressure reduction compared to losartan in head-to-head trials 4, 5, 6, 7

4. For resistant hypertension, escalate to triple therapy with an ARB + calcium channel blocker + thiazide diuretic, preferably as a single-pill combination 1, 8

Critical Safety Monitoring If Dual RAS Blockade Occurs

If a patient is inadvertently on both medications, immediately discontinue one agent and closely monitor: 3, 2

• Serum potassium levels (risk of life-threatening hyperkalemia)
• Renal function (serum creatinine, eGFR)
• Blood pressure (risk of symptomatic hypotension)

This is particularly dangerous in patients with chronic kidney disease, diabetes, elderly patients, or those on potassium supplements or potassium-sparing diuretics. 3, 2