Medically Reviewed on 10/24/2022

Brand Name: Cozaar

Generic Name: losartan

Drug Class: ARBs

What is losartan, and what is it used for?

Losartan is an oral medication that belongs to a class of drugs called angiotensin receptor blockers (ARBs). Other ARBs include irbesartan (Avapro), valsartan (Diovan), and candesartan (Atacand). Angiotensin formed in the blood by the action of angiotensin-converting enzyme (ACE) is a powerful chemical that attaches to angiotensin receptors found in many tissues but primarily on smooth muscle cells of blood vessels.

Angiotensin's attachment to the receptors causes the muscle cells to contract and the blood vessels to narrow (vasoconstrict) which leads to an increase in blood pressure (hypertension). Losartan (more specifically, the chemical formed when the liver converts the inactive losartan into its active form) blocks the angiotensin receptor. By blocking the action of angiotensin, losartan relaxes muscle cells and dilates blood vessels thereby reducing blood pressure.

Losartan is used for treating hypertension, reducing the risk of stroke in patients with hypertension, and left ventricular hypertrophy (overdeveloped heart muscle), and treating people with type 2 diabetes, and hypertensive patients with diabetic nephropathy (kidney disease). Losartan may be used alone or in combination with other drugs.

What are the side effects of losartan?

Side effects include:

Losartan also may cause:

Losartan may reduce kidney function in some patients and should not be used by patients who have bilateral renal artery stenosis (narrowing of both arteries going to the kidneys).

Rare cases of rhabdomyolysis (muscle breakdown) have been reported.

What is the dosage for losartan?

  • The starting dose of losartan for adults is 25-50 mg daily.
  • The maximum dose is 100 mg daily. The total daily dose of losartan may be divided and administered in two doses daily.
  • The starting dose of losartan for pediatric patients 6 years of age or older is 0.7 mg/kg up to 50 mg once daily. Doses more than 1.4 mg/kg or 100 mg daily have not been
  • Losartan may be given with or without food and may be evaluated in pediatric patients.


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Which drugs interact with losartan?

Losartan may increase levels of blood potassium (hyperkalemia), which can lead to serious heart problems (arrhythmias). Therefore, concomitant use of other drugs or substances that increase blood-such as potassium-sparing diuretics (for example, spironolactone [Aldactone], triamterene, and amiloride), potassium supplements, or salt substitutes containing potassium may lead to dangerous increases in serum potassium.

Combining losartan or other ARBs with nonsteroidal anti-inflammatory drugs (NSAIDs) in patients who are elderly, fluid-depleted (including those on diuretic therapy), or with poor kidney function may result in reduced kidney function, including kidney failure. These effects usually are reversible.

The antihypertensive effect of losartan may be reduced by aspirin and other NSAIDs such as:

Combining ARBs, ACE inhibitors, or aliskiren (Tekturna) increases the risk of hypotension (low blood pressure), and hyperkalemia, and reduces kidney function compared to each drug used alone and there is no additional benefit in preventing end-stage kidney disease or death.

Aliskiren and losartan should not be combined in patients with diabetes or renal impairment.

Increases in blood lithium (Eskalith, Lithobid) levels and lithium toxicity occurred when lithium and ARBa or hydrochlorothiazide were combined. Blood lithium levels should be monitored.

Is losartan safe to take if I'm pregnant or breastfeeding?

  • When used in the second or third trimester of pregnancy, ARBs can cause injury and even death to the fetus. Losartan should not be used during pregnancy. When pregnancy is first detected, losartan should be stopped.
  • It is not known whether losartan is excreted in breast milk, but losartan and its active form are excreted in rat milk. Due to the possibility of harm to the nursing infant, if possible, losartan should be discontinued by females who are nursing.


Losartan (Cozaar) is a medication prescribed for the treatment of high blood pressure. Losartan (Cozaar) belongs to a class of drugs referred to as ARBs (angiotensin receptor blockers). Side effects, drug interactions, warnings and precautions, and pregnancy and breastfeeding safety information should be reviewed prior to taking any medication.

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See more info: losartan on RxList
Medically Reviewed on 10/24/2022
FDA Prescribing Information