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Overview: Losartan is used for high blood pressure or in certain people with high blood pressure or diabetes. Common side effects may include dizziness, stuffy nose, or back pain. Do not drive or do other activities that require alertness or coordination until you know how losartan affects you. Serious side effects are less common, but may include low blood pressure, kidney problems, or high potassium levels in your blood. Contact your health care provider if you have confusion, muscle weakness, or feel unusually weak or tired while taking losartan. If you have trouble swallowing tablets, losartan is also available in a liquid form.  

Uses

What is losartan used for?

Losartan is commonly used for the following conditions.

  • To lower high blood pressure (hypertension) 
  • To lower the risk of stroke in people with high blood pressure and left ventricular hypertrophy, which is a type of heart problem
  • To protect the kidneys in people with type 2 diabetes and nephropathy, which is a type of kidney disease

Black people with both high blood pressure and left ventricular hypertrophy may not have a lower risk of stroke with losartan. 

Losartan may also be used for other conditions as determined by your health care provider.

How does losartan work (mechanism of action)?

Losartan blocks receptors in your body that normally bind to a hormone called angiotensin II. When angiotensin II binds to these receptors, it causes your blood vessels to constrict and the body to release a hormone that tells your kidneys to keep sodium. Blocking these receptors help your blood vessels relax so that blood can move through them more easily. Blocking these receptors also causes your body to get rid of sodium and water. These effects can help your heart work better, lower blood pressure, and may reduce your risk for heart attack, stroke, and kidney damage progression. 

How is losartan supplied (dosage forms)?

Brands and other names

  • Arbli
  • Cozaar

Dosage forms and strengths

  • 25 mg, 50 mg, 100 mg oral tablets
  • 10 mg/mL oral suspension

How should I store losartan?

Losartan should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C), for shorter periods of time, such as when transporting it. Store in a cool, dry place, in a tightly closed container. Protect from light.

Store liquid losartan in its original container. Throw away any unused medicine if it has been more than 60 days since the medicine was first opened.

Side Effects

What are the most common side effects of losartan?

The most common losartan side effects are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Dizziness
  • Infection in the nose or throat, sore throat, or common cold symptoms
  • Stuffy nose
  • Back pain

There may be other side effects of losartan that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of losartan?

While less common, the most serious side effects of losartan are described below, along with what to do if they happen.

Decreased Blood Pressure (Hypotension). Losartan may cause low blood pressure in people with low levels of fluids or salt. This can happen especially in people taking a medicine that causes you to pee more often (diuretic). If you feel faint or dizzy, lie down.Tell your health care provider right away if you have any of the following symptoms of low blood pressure.

  • Dizziness, feeling lightheaded, or fainting
  • Confusion
  • Feeling weak or tired

Kidney Damage.Kidney damage can happen when taking losartan. Call your health care provider right away if you have any of the following symptoms of kidney damage.

  • Reduced need to pee
  • Swelling in your feet, ankles, or legs
  • Weakness or unusual tiredness
  • Difficulty catching your breath or chest pain/pressure
  • Confusion
  • Nausea
  • Seizures 

High Potassium Level (Hyperkalemia). Losartan can cause a high potassium level (hyperkalemia), which can be serious and may lead to death. Your health care provider will check your potassium levels, especially if you take certain other medicines. Call your health care provider if you have any of the following symptoms of a high potassium level. 

  • Muscle weakness or unusual tiredness
  • Slow heartbeat or feeling of skipped heartbeats
  • Nausea or vomiting
  • Trouble breathing
  • Abnormal heart rhythm

Severe Allergic Reactions. Losartan may cause allergic reactions, which can be serious. Stop taking losartan and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use losartan?

Allergies to Ingredients. People who are allergic to any of the following should not take losartan.

  • Losartan
  • Arbli
  • Cozaar
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific losartan products they stock.

Drug Interactions. Losartan should not be taken while you are using certain other medicines. Before taking losartan, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

What should I know about losartan before using it?

Do not take losartan unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share losartan with other people, even if they have the same condition as you. It may harm them.

Keep losartan out of the reach of children.

Losartan can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how losartan affects you.

Use an accurate measuring device to measure your dose if you are taking the liquid form. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist what measuring device to use.

What should I tell my health care provider before using losartan?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if losartan is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Heart problems
  • Kidney problems
  • Liver problems
  • Electrolyte imbalance, such as high or low levels of sodium or potassium
  • Persistent or severe vomiting or diarrhea

Pregnancy. Losartan can cause death or serious harm to a fetus if taken during pregnancy. Tell your health care provider if you are pregnant, plan to become pregnant, or think you may be pregnant. If you get pregnant while taking losartan, stop taking it right away and contact your health care provider.

Breastfeeding. It is not known if losartan passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should stop breastfeeding or stop losartan. If you and your health care provider decide you should stop losartan, ask your health care provider how long you should wait after stopping it before you breastfeed your baby. 

Interactions

Does losartan interact with foods or drinks?

There are no known interactions between losartan and foods or drinks.

It is unknown if drinking alcohol will affect losartan. The risk of dizziness may be increased if you drink alcohol while taking losartan.

Does losartan interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking losartan.

  • Aliskiren (Tekturna), which is a medicine for high blood pressure 
  • A supplement or salt-substitute containing potassium
  • A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure
  • A nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen, naproxen, and others, which are contained in many prescription and OTC products for pain, swelling, and fever
  • Lithium, which is a medicine for certain mental health conditions
  • An angiotensin-converting enzyme (ACE) inhibitor, which is a medicine for high blood pressure, heart failure, and certain kidney problems
  • An angiotensin II receptor blocker (ARB), which is a medicine for high blood pressure, heart failure, and other heart conditions
  • Any medicine for high blood pressure

This may not be a complete list of medicines that can interact with losartan. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much losartan?

If you or someone else has used too much losartan, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of losartan?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take your next dose when your normally would. Do not take double or extra doses.