Losartan
Losartan is an angiotensin II receptor blocker (ARB) used to treat high blood pressure, protect kidneys in diabetic patients, and reduce stroke risk. It works by preventing blood vessels from narrowing.
About Losartan
Losartan is an angiotensin ii receptor blocker (arb) also known by the brand name Cozaar. It is primarily used to is prescribed to treat: • High blood pressure (hypertension) • Diabetic nephropathy (kidney disease in type 2 diabetics with high blood pressure) • Reduce the risk of stroke in patients with high blood pressure and left ventricular hypertrophy • Heart failure (sometimes used as alternative to ACE inhibitors) • Chronic kidney disease It helps protect organs from damage caused by high blood pressure. Losartan is available in oral tablet (25 mg, 50 mg, 100 mg) and oral combination tablet with hydrochlorothiazide (hyzaar — 50/12.5 mg, 100/12.5 mg, 100/25 mg) form. Healthcare providers commonly prescribe Losartan for conditions including Atrial Fibrillation, Attention Deficit Hyperactivity Disorder (ADHD), Hives (Urticaria), and Osteoarthritis.
Losartan at a Glance
- Brand names
- Cozaar
- Drug class
- Angiotensin II Receptor Blocker (ARB)
- Pregnancy category
- FDA Category Category D — Drugs acting on the renin-angiotensin system in the second and third trimesters cause fetal renal dysfunction, oligohydramnios, skull hypoplasia, and fetal death. Discontinue losartan as soon as pregnancy is detected and switch to a pregnancy-compatible antihypertensive. FDA Boxed Warning applies.
- Available forms
- Oral tablet (25 mg, 50 mg, 100 mg), Oral combination tablet with hydrochlorothiazide (Hyzaar — 50/12.5 mg, 100/12.5 mg, 100/25 mg)
- Therapeutic categories
- Cardiovascular, ARBs, Hypertension, Kidney Protection
- Conditions treated
- 8 related conditions on this site
What Losartan Is Used For
is prescribed to treat:
• High blood pressure (hypertension) • Diabetic nephropathy (kidney disease in type 2 diabetics with high blood pressure) • Reduce the risk of stroke in patients with high blood pressure and left ventricular hypertrophy • Heart failure (sometimes used as alternative to ACE inhibitors) • Chronic kidney disease
It helps protect organs from damage caused by high blood pressure.
Dosage Quick Reference
These are general dosage guidelines for Losartan. Your doctor will determine the appropriate dose for your specific situation.
| Condition | Starting Dose | Maintenance Dose |
|---|---|---|
| Hypertension (adults) | 50 mg once daily (25 mg in volume-depleted patients or hepatic impairment) | 25–100 mg/day, once daily or divided |
| Diabetic nephropathy with type 2 diabetes and proteinuria | 50 mg once daily | Titrate to 100 mg/day based on blood pressure response |
| Heart failure (alternative to ACE inhibitor) | 25 mg once daily | Double weekly as tolerated to target 150 mg/day in HEAAL trial; commonly 50–100 mg/day in practice |
| Stroke risk reduction in hypertension with LVH | 50 mg once daily | Add hydrochlorothiazide 12.5 mg or titrate losartan to 100 mg/day |
| Pediatric hypertension (>= 6 years) | 0.7 mg/kg (max 50 mg) once daily | Titrate up to 1.4 mg/kg/day (max 100 mg/day) |
Side Effects
Common side effects may include:
• Dizziness or lightheadedness • Upper respiratory infection symptoms • Back pain • Fatigue • Diarrhea • Stomach pain • Muscle cramps
Serious side effects (seek immediate medical attention):
• Signs of high potassium (irregular heartbeat, muscle weakness) • Signs of kidney problems (change in urine amount, swelling) • Severe dizziness or fainting • Signs of allergic reaction (rash, itching, swelling, difficulty breathing) • Chest pain • Symptoms of low blood pressure (severe dizziness, fainting, blurred vision)
See also: Drug Interactions ↓
Drug Interactions
Losartan is a prodrug converted to its active metabolite EXP3174 primarily through CYP2C9, with a minor CYP3A4 contribution. Most clinically important interactions stem from RAAS blockade and potassium handling.
- ACE inhibitors or aliskiren: Dual RAAS blockade increases the risk of hyperkalemia, hypotension, syncope, and acute kidney injury without consistent outcome benefit. Avoid combination, particularly in patients with diabetes or eGFR < 60 mL/min/1.73m².
- Potassium-sparing diuretics or potassium supplements (e.g., spironolactone, eplerenone, amiloride, potassium chloride, salt substitutes): Additive hyperkalemia risk. Monitor potassium periodically; avoid routine supplementation unless deficiency is documented.
- NSAIDs (e.g., ibuprofen, naproxen, celecoxib): Blunt antihypertensive effect of losartan and increase risk of acute kidney injury, especially in elderly or volume-depleted patients. Use the lowest dose for the shortest duration.
- Lithium: ARBs reduce renal lithium clearance and can precipitate lithium toxicity. Monitor lithium levels closely if combined.
- Strong CYP2C9 inhibitors (e.g., fluconazole, miconazole): May reduce conversion to the active metabolite, potentially attenuating blood pressure effect. Monitor blood pressure response when initiating these agents.
- Rifampin: Induces CYP enzymes and can reduce losartan exposure and effect. Monitor blood pressure and consider dose adjustment.
See also: Questions to Ask Your Doctor ↓
Key Considerations
Known drug interactions
Losartan has documented interactions with other medications, supplements, and certain foods. Review the Drug Interactions section below and tell your healthcare provider about every medication you take, including over-the-counter products. Jump to section →
Multiple forms available
Losartan comes in more than one form (Oral tablet (25 mg, 50 mg, 100 mg), Oral combination tablet with hydrochlorothiazide (Hyzaar — 50/12.5 mg, 100/12.5 mg, 100/25 mg)). The right form for you depends on your condition, ease of use, and your provider's recommendation.
Additional Information
What is ?
Losartan is a medication belonging to a class of drugs called angiotensin II receptor blockers (ARBs). It was the first ARB approved for use and remains one of the most commonly prescribed medications for high blood pressure and kidney protection.
How Does Losartan Work?
Losartan works by blocking the action of angiotensin II, a powerful chemical in the body that causes blood vessels to constrict:
- Blocks angiotensin II type 1 (AT1) receptors
- Prevents blood vessels from narrowing
- Lowers blood pressure
- Reduces workload on the heart
- Protects kidneys from damage
- Decreases aldosterone secretion (reduces sodium and water retention)
- May have uric acid-lowering effects
Unlike ACE inhibitors, losartan does not cause the buildup of bradykinin, which means it typically does not cause the persistent dry cough common with ACE inhibitors.
Common Uses
Losartan is prescribed for several conditions:
- Hypertension: First-line treatment for high blood pressure, used alone or with other medications
- Diabetic Nephropathy: Slows progression of kidney disease in type 2 diabetics with elevated creatinine and proteinuria
- Stroke Prevention: Reduces stroke risk in patients with hypertension and left ventricular hypertrophy
- Heart Failure: Alternative to ACE inhibitors for patients who develop cough
- Marfan Syndrome: May slow aortic root dilation (off-label use)
- Chronic Kidney Disease: Provides renoprotection
Dosage and Administration
Losartan is typically taken once or twice daily:
For Hypertension:
- Starting dose: 50 mg once daily
- May increase to 100 mg once daily
- Can be divided into twice-daily dosing
For Diabetic Nephropathy:
- Starting dose: 50 mg once daily
- Target dose: 100 mg once daily
Administration tips:
- Can be taken with or without food
- Take at the same time each day
- Continue taking even if you feel well
- May take 3-6 weeks for full blood pressure-lowering effect
- Can be used alone or combined with other blood pressure medications
Important Safety Information
Who Should Not Take Losartan?
Do not take losartan if you:
- Are allergic to losartan or any ARB
- Are pregnant (especially second and third trimesters)
- Are taking aliskiren (Tekturna) and have diabetes
- Have severe liver impairment
Drug Interactions
Inform your doctor about all medications, especially:
- Potassium supplements or salt substitutes containing potassium
- Other blood pressure medications
- NSAIDs (ibuprofen, naproxen) - may reduce effectiveness and harm kidneys
- Lithium - losartan may increase lithium levels
- Diuretics - especially potassium-sparing types
- Aliskiren - avoid combination in diabetics or kidney disease
- Rifampin - may decrease losartan effectiveness
Pregnancy Warning
⚠️ CRITICAL: Losartan can cause serious harm or death to an unborn baby if taken during the second or third trimester of pregnancy. If you become pregnant, stop taking losartan immediately and contact your doctor. Women of childbearing potential should use effective contraception.
Breastfeeding
It is not known if losartan passes into breast milk. Discuss with your doctor whether to discontinue breastfeeding or the medication.
Monitoring and Follow-Up
Your doctor will monitor:
- Blood pressure levels (home monitoring encouraged)
- Kidney function (creatinine, BUN, eGFR)
- Potassium levels (especially when starting or adjusting dose)
- Electrolytes
- Response to treatment
- For diabetic nephropathy: proteinuria/albumin in urine
Important: Blood tests are typically done:
- Before starting treatment
- 1-2 weeks after starting or dose increase
- Periodically during treatment
Special Populations
Kidney Disease:
- May be used to protect kidneys
- Dose adjustment usually not needed for mild-moderate kidney disease
- Monitor kidney function closely
- Small initial decline in kidney function is expected and acceptable
Liver Disease:
- Lower starting dose recommended (25 mg daily)
- Use with caution in severe liver disease
Elderly Patients:
- No dose adjustment needed
- May be more sensitive to blood pressure-lowering effects
- Monitor for dizziness and falls
Dehydration/Volume Depletion:
- Correct volume depletion before starting
- Risk of excessive blood pressure drop
Managing Side Effects
Dizziness/Lightheadedness
- Common when starting or increasing dose
- Rise slowly from sitting or lying position
- Stay well hydrated
- Usually improves with time
- Avoid alcohol
High Potassium
- Avoid potassium supplements unless prescribed
- Limit high-potassium foods if levels elevated
- Regular blood monitoring
- Especially important if taking potassium-sparing diuretics or have kidney disease
Lifestyle Considerations
To maximize benefits of losartan:
- Follow DASH diet or similar heart-healthy eating plan
- Reduce sodium intake (less than 2,300 mg daily, ideally 1,500 mg)
- Exercise regularly (150 minutes moderate activity per week)
- Maintain healthy weight
- Limit alcohol consumption
- Quit smoking
- Manage stress
- Monitor blood pressure at home
- Take medication consistently
Combination Therapy
Losartan is often combined with:
- Hydrochlorothiazide (HCTZ): Available as combination pill (Hyzaar) - enhances blood pressure control
- Amlodipine: Calcium channel blocker for additional blood pressure lowering
- Other diuretics: For improved blood pressure control or fluid management
Comparison with ACE Inhibitors
Advantages of Losartan over ACE Inhibitors:
- Does not cause dry cough
- Lower risk of angioedema (though still possible)
- Similar cardiovascular and kidney protection
- May be better tolerated
Similarities:
- Both protect kidneys in diabetes
- Both reduce cardiovascular events
- Both contraindicated in pregnancy
- Both can cause hyperkalemia and kidney function changes
When to Contact Your Doctor
Seek immediate medical attention if you experience:
- Severe dizziness or fainting
- Chest pain or irregular heartbeat
- Swelling of face, lips, tongue, or throat (angioedema - rare)
- Difficulty breathing or swallowing
- Severe stomach pain
- Dark urine or yellowing of skin/eyes
- Signs of high potassium (muscle weakness, slow heartbeat)
Contact your doctor for routine issues:
- Persistent dizziness
- Ongoing back pain
- Frequent upper respiratory infections
- Questions about blood pressure readings
- Planning pregnancy
- Scheduled surgery
Effectiveness and Benefits
Clinical studies demonstrate that losartan:
- Lowers blood pressure effectively in most patients
- Reduces stroke risk by 25% in high-risk hypertensive patients with left ventricular hypertrophy
- Slows progression of diabetic kidney disease
- Reduces proteinuria (protein in urine)
- Decreases hospitalization for heart failure
- Provides 24-hour blood pressure control with once-daily dosing
- May lower uric acid levels (beneficial in gout)
Storage
Store losartan at room temperature (77°F/25°C) with excursions permitted to 59-86°F (15-30°C). Protect from light and moisture. Keep in original container. Keep out of reach of children and pets.
Cost Considerations
Losartan is available as a generic medication, making it more affordable than some newer ARBs. It is covered by most insurance plans and available on many $4 generic lists.
Disclaimer: This information is for educational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment. Always consult your physician or other qualified healthcare provider with any questions about a medical condition or medication.
Frequently Asked Questions
Questions to Ask Your Doctor About Losartan
Consider discussing these topics at your next appointment:
- What blood pressure target are we aiming for, and how should I monitor it at home?
- How often should my kidney function and potassium be checked?
- Are any of my other medications going to interact with losartan?
- What symptoms of low blood pressure or high potassium should prompt a call?
- If losartan alone is not enough, what would the next step look like?
Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.