Can both telmisartan and losartan be taken together?

No, You Should Not Take Both Telmisartan and Losartan Together

Taking telmisartan and losartan simultaneously is not recommended and is potentially harmful. Both medications are angiotensin receptor blockers (ARBs) that work through the same mechanism, and combining them provides no additional cardiovascular benefit while significantly increasing the risk of serious adverse events.

Why This Combination Is Harmful

Guideline-Based Contraindication

The 2017 ACC/AHA Hypertension Guidelines explicitly state that simultaneous use of two ARBs is potentially harmful and is not recommended 1, 2. This is a Class III (Harm) recommendation with Level A evidence—the strongest level of evidence against a practice.

The 2024 ESC Guidelines similarly state that combining two RAS blockers (including two ARBs) is not recommended 3.

Evidence from Clinical Trials

The landmark ONTARGET trial provides the definitive evidence against dual RAS blockade 4, 5. This study of 25,620 patients compared:

• Telmisartan 80 mg alone
• Ramipril (an ACE inhibitor) alone
• The combination of both

Key findings:

• The combination provided no additional cardiovascular benefit compared to monotherapy
• The combination significantly increased adverse events:
  • Renal impairment: 13.5% vs 10.2%
  • Syncope: 0.3% vs 0.2%
  • Risk of dialysis, doubling of serum creatinine, or death increased by 9% (HR 1.09,95% CI 1.01-1.18)

FDA Drug Label Warning

The FDA-approved telmisartan label explicitly warns against dual RAS blockade 6:

• "In general, avoid combined use of RAS inhibitors"
• States that dual blockade is associated with increased risks of hypotension, hyperkalemia, and renal dysfunction compared to monotherapy
• Notes that "in most patients no benefit has been associated with using two RAS inhibitors concomitantly"

Specific Risks of Combining Two ARBs

Since both telmisartan and losartan are ARBs targeting the same receptor system, combining them creates:

1. Excessive RAS blockade without additional benefit
2. Increased risk of hyperkalemia (especially with CKD, diabetes, or potassium supplements)
3. Increased risk of acute renal failure (particularly in bilateral renal artery stenosis)
4. Increased risk of hypotension and syncope
5. No improvement in blood pressure control beyond what monotherapy achieves

What to Do Instead

If Blood Pressure Is Inadequately Controlled on One ARB:

Step 1: Optimize the dose of the single ARB

• Telmisartan: titrate up to 80 mg daily
• Losartan: titrate up to 100 mg daily

Step 2: Add a medication from a different class with complementary mechanism:

• First choice: Add a thiazide/thiazide-like diuretic (chlorthalidone 12.5-25 mg or hydrochlorothiazide 25-50 mg) 1, 2
• Second choice: Add a dihydropyridine calcium channel blocker (amlodipine 5-10 mg) 1, 2

Step 3: If still uncontrolled, use a three-drug combination:

• ARB + dihydropyridine CCB + thiazide diuretic (preferably as a single-pill combination) 3

Step 4: For resistant hypertension, add spironolactone 25-50 mg 1, 3

If Switching Between ARBs:

If you need to switch from losartan to telmisartan (or vice versa) for tolerability or efficacy reasons:

• Stop one ARB completely before starting the other
• Do not overlap the medications
• Research shows telmisartan may provide superior blood pressure control compared to losartan 7, 8, 9, but this is a switch, not a combination

Common Pitfall to Avoid

Do not assume that "more is better" with RAS blockade. The ONTARGET trial definitively proved that dual RAS blockade causes harm without benefit. This applies to:

• Two ARBs together (like telmisartan + losartan)
• ARB + ACE inhibitor together
• ARB or ACE inhibitor + direct renin inhibitor (aliskiren)

The only exception where dual therapy targeting similar pathways is acceptable is combining different types of diuretics (thiazide + potassium-sparing, or thiazide + loop diuretic) 1, 2.