Losartan Drug Interactions: What to Avoid and What to Tell Your Doctor

Losartan is generally well tolerated and has a reasonable drug interaction profile. But it does have clinically significant interactions with several common medications — including drugs many patients take daily. Knowing what to avoid, and what to discuss with your doctor, can help prevent serious problems.

This guide covers the most important drug interactions with losartan, organized by severity. Always share your complete medication list with your doctor and pharmacist — including vitamins, supplements, and over-the-counter drugs.

Major Interactions: Usually Avoid

Aliskiren (Tekturna) — Contraindicated in Diabetes

Aliskiren is a direct renin inhibitor sometimes used to treat high blood pressure. Combining it with losartan in patients with diabetes is contraindicated (absolutely not recommended). The combination significantly increases the risk of:

• Dangerously low blood pressure (hypotension)
• High potassium levels (hyperkalemia)
• Kidney problems, including acute kidney injury

This combination is also generally avoided in patients with kidney disease, even without diabetes.

ACE Inhibitors (Lisinopril, Enalapril, Ramipril, etc.)

Combining losartan with an ACE inhibitor is called "dual RAAS blockade" and is generally not recommended. The combination adds little additional blood pressure-lowering benefit but significantly increases the risk of low blood pressure, high potassium, and kidney impairment. This combination is rarely appropriate outside of specific specialist-directed regimens.

Moderate Interactions: Use With Caution

NSAIDs (Ibuprofen, Naproxen, Aspirin at High Doses)

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used medications worldwide — and they have a clinically significant interaction with losartan:

• Reduced blood pressure control: NSAIDs can blunt losartan's antihypertensive effect, making your blood pressure harder to control.
• Kidney damage risk: In patients who are dehydrated, elderly, on diuretics, or have kidney disease, taking NSAIDs with losartan significantly increases the risk of acute kidney injury.

If you need pain relief while on losartan, acetaminophen (Tylenol) is generally safer than NSAIDs for most patients. Ask your doctor what is appropriate for your situation.

Lithium

Losartan can increase the levels of lithium in the blood by reducing lithium excretion by the kidneys. Lithium has a narrow therapeutic window — too much causes toxicity. If you take both drugs, your doctor will monitor your lithium levels more frequently. Symptoms of lithium toxicity include nausea, tremor, confusion, and in severe cases, seizures.

Potassium Supplements and Potassium-Sparing Diuretics

Losartan raises potassium levels by blocking aldosterone (which normally causes potassium excretion). Taking it with:

• Potassium supplements
• Salt substitutes containing potassium (like No Salt or Nu-Salt)
• Potassium-sparing diuretics (spironolactone, eplerenone, triamterene, amiloride)

...can push potassium levels dangerously high (hyperkalemia). This is especially risky in patients with kidney disease, where the kidneys can't excrete excess potassium effectively. Symptoms include muscle weakness, irregular heartbeat, and potentially life-threatening cardiac arrhythmias.

CYP2C9 Inhibitors (Fluconazole, Amiodarone)

Losartan is metabolized in the liver by the CYP2C9 enzyme. Drugs that inhibit this enzyme (like fluconazole, an antifungal, or amiodarone, a heart rhythm drug) can increase losartan levels in the blood, potentially causing exaggerated blood pressure lowering.

Food Interactions

Losartan doesn't have a significant interaction with grapefruit (unlike some other cardiovascular medications). However:

• High-potassium foods: Patients with kidney disease or those taking other potassium-raising drugs should moderate potassium-rich foods (bananas, oranges, potatoes, avocados). For most healthy patients on losartan alone, normal dietary potassium is fine.
• Alcohol: Can enhance blood pressure lowering and cause increased dizziness or lightheadedness. Drink alcohol cautiously.

What to Tell Your Doctor and Pharmacist

Before starting losartan, tell your care team about all of the following:

• All prescription medications (especially other blood pressure drugs, lithium, diuretics)
• OTC medications (especially ibuprofen, naproxen, aspirin, antacids)
• Vitamins and supplements (especially potassium, magnesium, or herbal remedies)
• Any antifungal medications (fluconazole) or antibiotics (rifampin)
• Any recent illnesses involving vomiting, diarrhea, or dehydration

For more on what to watch for: Losartan Side Effects: What to Expect and When to Call Your Doctor

Or read the full medication guide: What Is Losartan? Uses, Dosage, and What You Need to Know in 2026.