Losartan (Cozaar)
An angiotensin II receptor blocker (ARB) widely used for high blood pressure and diabetic kidney disease. Unlike ACE inhibitors, losartan rarely causes a dry cough, making it a popular alternative.
What it's used for
Hypertension (high blood pressure), diabetic nephropathy (kidney protection in type 2 diabetes), and stroke risk reduction in patients with an enlarged heart. Sometimes prescribed for heart failure when ACE inhibitors aren't tolerated.
Typical dosing (adults)
- Starting: 50 mg once daily (25 mg if on a diuretic or liver problems).
- Range: 25–100 mg daily, in one or two doses.
- Can be taken with or without food, at the same time each day.
Key interactions
- Potassium supplements / salt substitutes: major — risk of dangerously high potassium (hyperkalemia).
- NSAIDs (ibuprofen, naproxen): moderate — can reduce blood pressure lowering effect and harm kidneys.
- Lithium: moderate — losartan can raise lithium levels to toxic range.
- Aliskiren (Tekturna): major — do not combine, especially with diabetes or kidney disease.
- Rifampin: moderate — speeds breakdown of losartan's active form, reducing effectiveness.
Common side effects
Dizziness or lightheadedness (especially when starting or increasing dose), elevated potassium, mild fatigue. Upper respiratory infections and back pain are reported. Rare but serious: angioedema (facial/throat swelling) — far less common than with ACE inhibitors, but seek emergency care immediately.
Who should be cautious
- Pregnancy (do not use — can cause serious harm to an unborn baby; switch before conception).
- Severe liver disease (lower starting dose needed).
- Bilateral renal artery stenosis.
- People already taking an ACE inhibitor or aliskiren.
What to ask your pharmacist
- Can I use potassium-containing salt substitutes while on losartan?
- How often should I get my kidney function and potassium levels checked?
- Is it safe to take ibuprofen occasionally for pain relief?
- I'm planning a pregnancy — when should I stop losartan?