What Is Losartan and How Does It Work?

Losartan is used to treat high blood pressure and to help protect the kidneys from damage due to diabetes. It is also used to lower the risk of strokes in patients with high blood pressure and an enlarged heart. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Losartan belongs to a class of drugs called angiotensin receptor blockers (ARBs). It works by relaxing blood vessels so that blood can flow more easily.

Losartan is available under the following different brand names: Cozaar.

What are Dosages of Losartan?

Dosages of Losartan include the following:

Adult and pediatric dosages

  • Injectable solution
  • Tablet
    • 25 mg
    • 50 mg
    • 100 mg

Dosage Considerations -- Should Be Given As Follows:

Adult dosage considerations

  • Hypertension
    • 50 mg/day orally (25 mg/day in patients with possible intravascular depletion or receiving diuretics)
    • Dosage range: 25-100 mg/day orally in 1 or 2 daily doses
  • Diabetic Nephropathy
  • Type 2 diabetes and hypertension:
    • 50-100 mg orally once/day
  • Hypertension and Left Ventricular Hypertrophy
    • 50 mg orally once/day initially; may increase to 100 mg orally once/day; may use in combination with a thiazide diuretic

Dosage Considerations

  • Generally, adjust dosage monthly; adjust more aggressively in high-risk patients

Pediatric dosage considerations

  • Under 6 years of age:
    • Safety and efficacy not established
  • 6 years and older:
    • 0.7 mg/kg per day (up to 50 mg/per day) orally initially, not to exceed 1.4 mg/kg per day (or 100 mg/day)
    • Oral suspension may be used

What Are Side Effects Associated with Using Losartan?

Side effects of losartan include:

Other side effects of Losartan include:


  • heart rate irregularities (including ventricular and supraventricular tachycardia, premature ventricular contractions, and atrial fibrillation)
  • slow heart rate
  • electrocardiographic alterations (including second-degree heart block, QT/QTc interval prolongation, and ST segment depression)
  • palpitations
  • fainting (rarely and predominantly with intravenous losartan)
  • transient ECG changes including QT/QTc interval prolongation have been reported


  • nausea
  • vomiting


  • ECG alterations: heartbeat irregularities; prolongation of PR, QRS, and QT intervals


  • specific hepatic enzyme abnormalities
  • hepatic necrosis
  • abnormal hepatic function


  • flushing
  • rare cases of hypersensitivity reactions, sometimes severe (acute allergic reactions, rapid swelling, difficulty breathing, cardiopulmonary arrest, low blood pressure, laryngeal edema, laryngospasm, shock, shortness of breath, or stridor)

Local reactions

  • pain, redness, and burning at the injection site

Lower respiratory

  • involuntary intermittent or sustained deviation of the eyes, appearing alone, as well as with other dystonic reactions; transient dizziness during or shortly after intravenous infusion

Skin and subcutaneous tissue

Eye Disorders

  • Transient blindness (predominantly during IV administration) was reported to resolve within a few minutes up to 48 hr;
  • transient blurred vision

Musculoskeletal and connective tissue

  • joint pain

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Losartan?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Severe Interactions of Losartan include:
    • aliskiren
  • Serious Interactions of Losartan include:
  • Losartan has moderate interactions with at least 156 different drugs.
  • Losartan has minor interactions with at least 29 different drugs.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Losartan?


  • Discontinue as soon as possible when pregnancy is detected; drug affects the renin-angiotensin system, causing oligohydramnios, which may result in fetal injury or death
  • This medication contains losartan. Do not take Cozaar if you are allergic to losartan or any ingredients contained in this drug
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Hypersensitivity
  • Coadministration with aliskiren in patients with diabetes mellitus

Effects of Drug Abuse

  • None

Short-Term Effects

  • Increases risks of low blood pressure and abnormal potassium levels in the blood
  • See also "What Are Side Effects Associated with Using Losartan?”

Long-Term Effects

  • See also "What Are Side Effects Associated with Using Losartan?”


  • Rapid swelling, volume-depletion, severe congestive heart failure, hepatic or renal impairment
  • Correct volume or salt depletion before administration
  • Increases risks of low blood pressure and abnormal potassium levels in the blood
  • Monitor renal function and potassium levels in susceptible patients
  • Discontinue immediately if the patient is pregnant; the potential risk of congenital malformations
  • Use with caution in renal artery stenosis, and avoid bilateral renal artery stenosis
  • Renal impairment reported
  • Increased heart failure-related morbidity in patients receiving angiotensin-converting enzyme inhibitors (ACE inhibitors) and beta-blockers concomitantly; such combination therapy is not recommended
  • Dual blockade of the renin-angiotensin-aldosterone system (an angiotensin-receptor blocker [ARB] plus an ACE inhibitor) in patients with established atherosclerotic disease, heart failure, or diabetes with end-organ damage is associated with a higher frequency of low blood pressure, fainting, abnormal potassium levels, and altered renal function (including acute renal failure) in comparison with the use of a single renin-angiotensin-aldosterone system agent; limit dual blockade to individually defined cases with close monitoring of renal function; closely monitor blood pressure
  • Risk of severe allergic reactions or rapid swelling

Pregnancy and Lactation with Losartan

  • Use losartan in LIFE-THREATENING emergencies when no safer drug is available. There is positive evidence of human fetal risk
  • The use of losartan or other drugs that act on the renin-angiotensin system during the 2nd and 3rd trimesters of pregnancy reduces renal function and increases fetal and neonatal morbidity and death. The resulting levels of low amniotic fluid can be associated with fetal lung underdevelopment and skeletal deformations. Potential neonatal adverse effects include skull underdevelopment, failure of the kidneys to produce urine, low blood pressure, kidney failure, and death
  • When pregnancy is detected, discontinue losartan as soon as possible
  • It is unknown if losartan is excreted in the milk; therefore use of losartan is not recommended when lactating. Consult with a physician

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