Losartan

Generic Name: Losartan

Brand Names: Cozaar

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.

CardiovascularARBsHypertensionKidney Protection

Drug Class

Angiotensin II Receptor Blocker (ARB)

Pregnancy

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)

What It's 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. 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)

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.

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

Some blood pressure reduction is typically seen within the first week, but the full effect develops over 3 to 6 weeks. Your doctor will usually recheck readings 2 to 4 weeks after starting or increasing the dose, often combining clinic measurements with a home blood pressure log.

Losartan and other ARBs achieve similar blood pressure and kidney-protective effects without the persistent dry cough that affects 5 to 20 percent of patients on ACE inhibitors, and with a lower (though not zero) risk of angioedema. ARBs are commonly chosen first when these side effects are likely to be problematic.

ARBs can raise serum potassium because they reduce aldosterone signaling. For most patients with normal kidney function this is mild and well tolerated. Patients with chronic kidney disease, diabetes, or those on other potassium-elevating drugs need periodic blood tests. Avoid potassium-based salt substitutes unless your doctor approves them.

Take the missed dose as soon as you remember on the same day. If it is nearly time for your next dose, skip the missed dose and continue your regular schedule. Do not double up. Consistent daily timing — for example, with breakfast or at bedtime — improves both adherence and 24-hour blood pressure control.

Occasional short use of ibuprofen or naproxen is usually fine for healthy adults, but regular daily NSAID use can blunt losartan effect and raise the risk of kidney injury — especially in older adults or during dehydration, which is common in Florida heat. Acetaminophen is generally a safer first option for routine pain or fever.

Questions to Ask Your Doctor

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?

Schedule an Appointment

Related Health Conditions

This medication is commonly used to treat or manage the following conditions:

Atrial Fibrillation

Atrial fibrillation, a common arrhythmia characterized by rapid, irregular heartbeats, increases risk of stroke and heart failure, often linked to age, hypertension, and heart disease.

Learn More

Attention Deficit Hyperactivity Disorder (ADHD)

ADHD is a neurodevelopmental disorder marked by inattention, hyperactivity, and/or impulsivity, stemming from complex interactions between genetics, brain differences, and environmental factors, not poor parenting.

Learn More

Hives (Urticaria)

Hives (urticaria) are itchy, raised welts caused by histamine release, triggered by allergens, physical stimuli, medications, infections, stress, or sometimes, unknown factors.

Learn More

Osteoarthritis

Osteoarthritis, a common degenerative joint disease, causes pain, stiffness, and reduced motion due to cartilage breakdown from aging, genetics, obesity, injuries, or repetitive stress.

Learn More

Portal Hypertension

Portal hypertension, an elevated pressure in the portal vein due to blockage often from cirrhosis or other pre-hepatic causes, can lead to serious complications like bleeding and ascites.

Learn More

Secondary Pulmonary Hypertension

Secondary pulmonary hypertension, unlike its primary form, arises from underlying conditions such as heart/lung disease, blood clots, or connective tissue disorders, increasing lung artery pressure.

Learn More

Stroke

A stroke, caused by interrupted brain blood supply from blockage (ischemic) or bleeding (hemorrhagic), is a medical emergency requiring prompt treatment to minimize brain damage.

Learn More

Vertigo

Vertigo, a spinning sensation distinct from dizziness, often stems from inner ear or brain issues like BPPV or Meniere's, sometimes triggered by head trauma or medication.

Learn More

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.