Losartan (patient information)
Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Losartan is used alone or in combination with other medications to treat high blood pressure. Losartan is in a class of medications called angiotensin II receptor antagonists. It works by blocking the action of certain chemicals that tighten the blood vessels so blood flows more smoothly.
Do not take losartan if you are pregnant. If you become pregnant while taking losartan, call your doctor immediately. Losartan may harm the fetus.
How this medication should be used
Losartan comes as a tablet to take by mouth. It is usually taken once or twice a day with or without food. To help you remember to take losartan, take it around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take losartan exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Losartan controls high blood pressure but does not cure it. Continue to take losartan even if you feel well. Do not stop taking losartan without talking to your doctor.
Other uses for this medicine
Losartan is also used sometimes to treat congestive heart failure. Talk to your doctor about the possible risks of using this medication for your condition.
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
Before taking losartan:
- tell your doctor and pharmacist if you are allergic to losartan or any other medications.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: diuretics ('water pills'), indomethacin (Indocin), and potassium supplements. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
- tell your doctor if you have or have ever had heart failure or kidney or liver disease.
- tell your doctor if you plan to become pregnant or are breast-feeding.
Special dietary instructions
Talk to your doctor before using salt substitutes containing potassium. If your doctor prescribes a low-salt or low-sodium diet, follow these directions carefully.
What to do if you forget a dose
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular regular dosing schedule. Do not take a double dose to make up for a missed one.
Minor Side Effects
Losartan may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- runny nose
- sore throat
Severe Side Effects
Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them, call your doctor immediately:
- swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
- difficulty breathing or swallowing
Losartan may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/MedWatch/report.htm] or by phone [1-800-332-1088].
Storage conditions needed for this medication
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
Symptoms of overdose may include:
- rapid or pounding heartbeat
Keep all appointments with your doctor. Your blood pressure should be checked regularly to determine your response to losartan.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
Brand names of combination products
- Hyzaar® (containing Losartan Potassium and Hydrochlorothiazide)