What drugs should not be taken with losartan? A comprehensive guide to interactions

October 12, 2025 •

4 min read

Over 1.5 million prescriptions for losartan were filled in 2022, but not all patients are aware of its serious drug interactions. Understanding what drugs should not be taken with losartan? is essential to prevent adverse effects like dangerous electrolyte imbalances and kidney damage.

Quick Summary

Losartan can interact with certain medications and supplements, increasing the risk of serious side effects like high potassium levels, kidney damage, or low blood pressure. Interactions with NSAIDs, potassium-sparing diuretics, lithium, and other blood pressure drugs are particularly significant.

Key Points

Avoid NSAIDs: Chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen with losartan can increase the risk of kidney damage and reduce losartan's effectiveness.
Monitor Potassium Levels: Losartan can cause high blood potassium (hyperkalemia), a risk significantly amplified by potassium-sparing diuretics (e.g., spironolactone) and potassium supplements.
Never Combine Losartan and ACE Inhibitors: The simultaneous use of losartan with ACE inhibitors (e.g., lisinopril) or aliskiren creates a dangerous 'dual blockade' that increases side effects without added benefit.
Be Cautious with Lithium: Taking losartan and lithium together requires close medical supervision, as losartan can cause lithium levels to rise to toxic levels.
Inform Your Doctor About All Medications: It is crucial to inform your doctor and pharmacist about all medications, supplements, and vitamins you are taking to prevent harmful interactions.
Avoid Losartan During Pregnancy: Losartan has an FDA boxed warning for fetal toxicity and should be discontinued immediately if pregnancy is detected.

Introduction to Losartan and Why Interactions Matter

Losartan is a medication used to treat high blood pressure, reduce the risk of stroke in certain patients, and manage kidney disease in people with type 2 diabetes. It is an angiotensin II receptor blocker (ARB) that works by relaxing blood vessels, allowing for better blood flow. However, because it affects the body's cardiovascular and renal systems, it can have significant and sometimes dangerous interactions with other medications, foods, and supplements. A comprehensive understanding of these interactions is vital for anyone taking losartan to ensure their safety and the treatment's effectiveness.

What drugs should not be taken with losartan?

Losartan, and other ARBs, must be used with caution, or altogether avoided, with several classes of drugs. Taking these combinations can lead to a range of complications, including dangerously high potassium levels (hyperkalemia), kidney failure, and reduced medication effectiveness.

Potassium-sparing diuretics and supplements

Losartan and potassium-sparing diuretics both increase the levels of potassium in the blood by preventing its excretion. The combination can cause hyperkalemia, which can lead to life-threatening cardiac arrhythmias.

Drugs to avoid or use with caution:

Spironolactone (Aldactone): Often used for heart failure and hypertension, combining it with losartan requires very close monitoring.
Triamterene (Dyrenium) and amiloride (Midamor): These are other common potassium-sparing diuretics.
Potassium supplements and salt substitutes: Many salt substitutes contain potassium chloride instead of sodium chloride. Patients should avoid both potassium supplements and these substitutes unless specifically directed by a doctor.

Nonsteroidal anti-inflammatory drugs (NSAIDs)

For patients on losartan, particularly those who are elderly, dehydrated, or have pre-existing kidney problems, combining with NSAIDs poses a significant risk.

Reasons to avoid NSAIDs:

Reduced efficacy: NSAIDs can counteract the blood pressure-lowering effect of losartan.
Kidney damage: Both drugs can independently affect kidney function, so taking them together increases the risk of acute kidney injury.

Common NSAID examples include:

Ibuprofen (Advil, Motrin)
Naproxen (Aleve, Naprosyn)
Celecoxib (Celebrex)
Meloxicam (Mobic)

ACE inhibitors and aliskiren

Combining losartan with an ACE inhibitor (like lisinopril or ramipril) or a direct renin inhibitor (like aliskiren) is known as 'dual blockade' of the renin-angiotensin system (RAAS). This combination is generally avoided because it significantly increases the risks of hypotension (low blood pressure), hyperkalemia, and kidney dysfunction without offering additional cardiovascular benefits.

Important warnings:

Lisinopril (Zestril) and Enalapril (Vasotec): Do not take an ACE inhibitor with losartan.
Aliskiren (Tekturna): This combination is contraindicated, especially for patients with diabetes or kidney impairment.

Lithium

Losartan can affect the kidneys' ability to excrete lithium, a medication used to treat bipolar disorder. This can lead to increased lithium levels in the blood, causing potentially life-threatening lithium toxicity. Symptoms can include confusion, tremors, blurred vision, and muscle weakness. Patients taking both medications require careful and frequent monitoring of their lithium levels.

Comparison of Losartan Interactions


Interacting Drug Class	Examples	Primary Risk	Key Monitoring or Action Required
Potassium-sparing Diuretics	Spironolactone, Triamterene	Hyperkalemia (high blood potassium)	Frequent serum potassium level checks; dose adjustment or alternative medication
NSAIDs	Ibuprofen, Naproxen, Celecoxib	Reduced losartan effectiveness, kidney damage	Avoid chronic use; consider alternative pain relief; monitor blood pressure and kidney function
ACE Inhibitors / Aliskiren	Lisinopril, Enalapril, Aliskiren	Severe hypotension, hyperkalemia, kidney damage	Combination is generally avoided due to increased risks without added benefit
Lithium	Lithium (Lithobid)	Lithium toxicity due to increased blood levels	Regular monitoring of lithium levels; potential dose adjustment
Potassium Supplements	Potassium chloride, salt substitutes	Hyperkalemia (high blood potassium)	Avoid unless specifically instructed and monitored by a doctor

Additional warnings and precautions

Beyond specific drug classes, patients taking losartan should also be aware of other factors that can influence their safety:

Pregnancy: Losartan has a boxed warning from the FDA against its use during pregnancy, especially during the second and third trimesters, due to the risk of fetal harm or death.
Pre-existing conditions: Patients with pre-existing kidney disease, liver problems, or dehydration should use losartan with extreme caution and under close medical supervision.
Grapefruit: Some sources suggest grapefruit and grapefruit juice may affect losartan levels, potentially making the drug less effective. It is best to discuss consumption with a doctor.
Signs of an interaction: Watch for symptoms of high potassium (nausea, weakness, irregular heartbeat), kidney issues (reduced urination, swelling), or lithium toxicity (tremors, confusion).

What to do if you are taking interacting medications

If you find that you are taking losartan alongside one of the interacting medications, do not stop taking any medication without consulting your doctor first. Your healthcare provider may recommend a change in dosage, an alternative medication, or a more intensive monitoring plan. They will consider your overall health and the severity of the potential interaction.

Conclusion: Navigating losartan safely

Taking losartan safely requires careful attention to other medications and supplements you consume. The potential for serious complications, such as hyperkalemia from potassium-sparing diuretics or kidney damage from NSAIDs, makes a thorough understanding of interactions crucial. Always keep your healthcare team informed of all prescription, over-the-counter, and herbal products you use. By being proactive and maintaining open communication with your doctor, you can manage your condition effectively and minimize risks. For more detailed information on specific medications, consult resources like the FDA-approved prescribing information or talk to a pharmacist.

Visit the U.S. Food and Drug Administration for Drug Information

Frequently Asked Questions

You should generally avoid taking NSAIDs like ibuprofen or naproxen with losartan, especially for prolonged periods, as this can increase the risk of kidney problems and make losartan less effective at lowering blood pressure.

Potassium-sparing diuretics, such as spironolactone and triamterene, cause the body to retain potassium. When combined with losartan, this can lead to dangerously high potassium levels (hyperkalemia) in the blood, which can affect heart rhythm.

Yes, you should avoid potassium supplements and salt substitutes that contain potassium, as they can cause hyperkalemia when combined with losartan. Always check the labels of any supplements and consult your doctor.

Combining losartan with other medications in the same class, like ACE inhibitors (e.g., lisinopril) or aliskiren, is generally not recommended and should be avoided due to the increased risk of severe side effects.

Symptoms of high potassium can include muscle weakness, fatigue, numbness or tingling, nausea, and heart palpitations. You should contact your doctor immediately if you experience these symptoms.

Some sources suggest that grapefruit and grapefruit juice may decrease the effectiveness of losartan. It is best to consult your doctor about your diet to understand the potential risks.

If you remember that you are taking an interacting medication, you should inform your doctor or pharmacist as soon as possible. Do not stop or change any medication without their guidance.