Approved indications: Losartan is approved to treat hypertension in adults and children 6 years and older, to reduce the risk of stroke in adults with hypertension and left ventricular hypertrophy, and to treat diabetic nephropathy in adults with type 2 diabetes, hypertension, and proteinuria.

Off-label uses and evidence: Clinicians may use losartan off-label for heart failure with reduced ejection fraction in patients who cannot tolerate ACE inhibitors, for proteinuric chronic kidney disease not due to diabetes, and for certain conditions with aortic dilation (such as some connective tissue disorders), based on clinical trials and guideline support that provide moderate to high levels of evidence for ARBs in these settings.

Efficacy expectations: Blood pressure usually starts to improve within about 1 week, with full effect often reached in 3–6 weeks, and most people experience reductions similar to those seen with other ARBs and ACE inhibitors. In diabetic kidney disease and other proteinuric kidney conditions, losartan can reduce protein in the urine and slow loss of kidney function over months to years. Stroke-risk reduction and heart- and kidney-protective benefits are seen over long-term use, and overall its blood pressure–lowering and organ-protective efficacy is comparable to other drugs in the same class, with generally better tolerability than ACE inhibitors because it causes less cough and angioedema.

Typical adult dosing: For hypertension, the usual starting dose is 50 mg by mouth once daily, with a typical range of 25–100 mg per day given once daily or divided into two doses; for diabetic nephropathy and for stroke-risk reduction with left ventricular hypertrophy, 50 mg once daily is often started and may be increased to 100 mg once daily as tolerated and needed for blood pressure and kidney protection.

Pediatric dosing (6–16 years): For children with hypertension who can swallow tablets, the typical starting dose is 0.7 mg/kg once daily (up to 50 mg), which may be adjusted up to a maximum of 1.4 mg/kg (not exceeding 100 mg) once daily, based on response and tolerability.

How to take it: Losartan tablets can be taken with or without food, at the same time each day, swallowed with water without crushing or chewing unless a prescriber advises otherwise. In people with low blood volume, liver impairment, or certain other conditions, a lower starting dose such as 25 mg once daily may be used.

Special dosing instructions: Dose adjustments may be needed in those taking diuretics, in people with kidney or liver problems, and when losartan is combined with other blood pressure medicines. Clinicians may combine losartan with a thiazide diuretic or other agents if a single drug does not adequately control blood pressure.

Missed dose: If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose; in that case, skip the missed dose and resume the regular schedule without doubling up.

Overdose: Taking too much losartan can cause marked low blood pressure, dizziness, or fainting, and sometimes changes in heart rate or kidney function; emergency medical care and contact with a poison control center should be sought immediately in case of suspected overdose.

Common side effects: The most frequent side effects include dizziness or lightheadedness (especially when first starting or increasing the dose), fatigue, low blood pressure, nasal congestion or upper respiratory symptoms, and changes in kidney function or blood potassium; these are usually mild to moderate and often improve as the body adjusts.

Serious or rare adverse effects: Seek urgent medical attention for signs of severe allergic reaction or angioedema (such as swelling of the face, lips, tongue, or throat, or trouble breathing), very low blood pressure with fainting, markedly decreased urine output, severe or worsening shortness of breath, chest pain, or symptoms of high potassium (such as muscle weakness, unusual heartbeats, or palpitations).

Warnings and precautions: Losartan can harm or kill an unborn baby and should not be used during pregnancy; people who become pregnant while taking it should stop it promptly and contact their clinician. Use is generally not recommended during breastfeeding because data are limited and other medicines may be preferred. Extra caution and possible dose adjustments are needed in people with kidney disease, liver impairment, dehydration, heart failure, or narrowing of the kidney arteries, and in older adults who may be more sensitive to blood pressure drops and changes in kidney function.

Safety compared with similar drugs: Compared with ACE inhibitors, losartan and other ARBs cause less cough and usually less angioedema, but share similar risks of low blood pressure, kidney function changes, and high potassium; overall, losartan is considered a well-tolerated long-term blood pressure medicine for most patients when appropriately monitored.

Reporting side effects and safety updates: Side effects and concerns can be reported to the U.S. FDA MedWatch program (online or by phone), and up-to-date safety communications are available through FDA safety alerts and medication guides provided with the prescription.

Drug and supplement interactions: Losartan can interact with other medicines that affect the renin–angiotensin system (such as ACE inhibitors, other ARBs, and aliskiren), increasing the risk of low blood pressure, kidney problems, and high potassium; combining it with aliskiren is generally avoided, especially in people with diabetes. Potassium-sparing diuretics, potassium supplements, and salt substitutes containing potassium can raise potassium levels further and should be used only with close monitoring. Nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce the blood pressure effect of losartan and increase the risk of kidney problems, particularly in older adults or those with kidney disease or dehydration. Losartan can also increase lithium levels, so concurrent use requires caution and monitoring of lithium concentrations.

Food, alcohol, and other interactions: Losartan does not have major food restrictions and may be taken with or without meals, but alcohol can enhance blood pressure–lowering effects and dizziness, so moderation and caution are advised. There are no specific interactions with common imaging contrast agents, but because contrast dyes can affect kidney function, clinicians often monitor kidney health more closely in people taking losartan.

Conditions requiring caution: Use is cautious or may be avoided in people with a history of angioedema to ARBs, significant kidney artery narrowing, severe kidney impairment, liver disease, very low blood pressure, or volume depletion (such as from heavy diuretic use, vomiting, or diarrhea). It should not be used during pregnancy and is usually avoided or used with caution while breastfeeding.

Monitoring needs: Regular monitoring typically includes blood pressure checks and periodic blood tests to assess kidney function (such as serum creatinine) and electrolytes (especially potassium), particularly after starting therapy or changing the dose, and in people with kidney disease, diabetes, or those taking interacting drugs.

Q: How long does it take for losartan to start lowering my blood pressure?
A: Many people see some blood pressure improvement within about 1 week of starting losartan, with the full effect usually reached after 3–6 weeks of regular daily use.

Q: Is losartan safe to take during pregnancy or while trying to conceive?
A: Losartan should not be used during pregnancy because it can seriously harm an unborn baby, and people planning pregnancy are usually switched to another blood pressure medicine before trying to conceive.

Q: Can I drink alcohol while taking losartan?
A: Moderate alcohol use is not strictly prohibited, but alcohol can increase dizziness and the blood pressure–lowering effect of losartan, so it is best to limit intake and stand up slowly until you know how the combination affects you.

Q: What should I do if I feel dizzy after taking losartan?
A: Sit or lie down until the dizziness passes, rise slowly, and drink fluids if you are not restricted; if dizziness is severe, persistent, or associated with fainting, chest pain, or shortness of breath, contact a clinician promptly.

Q: Is losartan the same as Cozaar?
A: Cozaar is a brand name for losartan potassium, so both contain the same active ingredient, although generic losartan may be supplied by different manufacturers.

Storage: Keep losartan tablets at room temperature, away from excess heat, moisture, and direct light, in their original tightly closed container, and out of reach of children and pets.

Disposal: Use a community drug take-back program if available; if none is accessible, mix unused tablets with an undesirable substance (such as used coffee grounds or cat litter), place the mixture in a sealed bag or container, and throw it in the household trash, removing or scratching out personal information on prescription labels before discarding bottles and boxes.