Losartan - an angiotensin receptor blocker (Cozaar)

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Take losartan once each day. You can take your doses either before or after a meal.

Any side-effects are usually mild, and can include feeling dizzy or light-headed.

Some painkillers can interfere with losartan and increase the risk of side-effects, so ask a pharmacist for advice before you buy any medicines 'over the counter'.
Type of medicineAn angiotensin-II receptor antagonist
Used forHigh blood pressure; heart failure; kidney disease associated with diabetes
Also calledCozaar® and Cozaar-Comp® (which also contains hydrochlorothiazide)
Available asTablets and oral liquid suspension

Losartan is an angiotensin receptor blocker. It is also called an angiotensin-II receptor antagonist, or an AIIRA. You will have been prescribed losartan for one of the following reasons:

Losartan works by blocking the effect of a substance in your body called angiotensin II. Angiotensin II causes your blood vessels to narrow and also leads to the production of another substance called aldosterone, which increases the amount of fluid in your blood. By preventing the action of angiotensin II, losartan reduces how much work your heart has to do and lowers your blood pressure. It also has a protective effect on your kidneys.

You may be prescribed losartan to take on its own, or alongside other medicines to help your condition. There is a combination tablet available called Cozaar-Comp® which contains losartan with a diuretic called hydrochlorothiazide. This combination tablet can be prescribed to people with high blood pressure to help reduce the total number of tablets that need to be taken each day.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking losartan it is important that your doctor knows:

  • If you are pregnant or breast-feeding.
  • If you know you have a blockage of the artery which supplies blood to your kidneys, a condition called renal artery stenosis.
  • If you have any problems with your heart valves or heart muscle.
  • If you have a problem with the way your liver works.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine, or if you have had any other type of allergic reaction.
  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about losartan and will provide you with a full list of the side-effects which you could experience from taking it.
  • Take losartan once each day, exactly as your doctor tells you to. There are several different strengths of tablet available. When you first start treatment your doctor may gradually increase the strength of the tablets to suit your condition. Each time you collect a fresh supply, it's a good idea to check the strength on the packet to make sure they are what you are expecting.
  • Try to take losartan at the same time of day each day. For most people this will be in the morning. Taking your doses at the same time each day will help you to remember to take losartan regularly.
  • Swallow the tablet with a drink of water. You can take losartan either before or after a meal.
  • If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, miss out the forgotten dose. Do not take two doses at the same time to make up for a forgotten dose.
  • Try to keep your regular appointments with your doctor. This is so your progress can be monitored. Your doctor may want you to have some blood tests from time to time to check on your kidneys, and also how much potassium is in your blood.
  • If you buy any medicines, check with a pharmacist that they are suitable to take with losartan. This is because some anti-inflammatory painkillers (such as aspirin and ibuprofen) can interfere with the way it works, and also may increase the risk of side-effects.
  • It is very important that you follow any dietary and lifestyle advice that you have been given by your doctor, such as eating a healthy diet, not smoking, and taking regular exercise.
  • If you drink alcohol, ask your doctor for advice. Your doctor may recommend that you do not drink alcohol while you are on losartan because it will increase the risk of side-effects, such as feeling dizzy or faint.
  • Try to avoid salt substitutes which contain potassium. This is because the substitutes will increase the amount of potassium in your blood and this can cause problems.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking losartan. This is because your blood pressure may drop too low if you are given some anaesthetics.
  • Treatment with losartan is usually long-term unless you experience an adverse effect. Continue to take the tablets regularly, unless you are advised otherwise by your doctor.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with losartan. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common losartan side-effects (these affect less than 1 in 10 people)What can I do if I experience this?
Feeling tired, or dizzy and light-headed when you stand up (due to low blood pressure)Getting up and moving more slowly should help. If you begin to feel dizzy, sit for a few minutes before you stand up again
Changes in the amount of potassium in your bloodYou will have blood tests from time to time to check for this

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.
  • Store the tablets in a cool, dry place, away from direct heat and light.
  • Store the liquid medicine in a refrigerator and do not use it after the expiry date on the bottle. The expiry date is four weeks after it has been made up by the pharmacy.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital at once. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
993 (v27)
Last Checked:
03/02/2016
Next Review:
02/02/2019
The Information Standard - certified member

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