Health Centres - Cibral (isosorbide mononitrate)
How does it work?
Cibral tablets contain the active ingredient isosorbide mononitrate, which is a type of medicine called a nitrate. It is used to help the heart work more easily. (NB. Isosorbide mononitrate tablets are also available without a brand name, ie as the generic medicine.)
Isosorbide mononitrate works by being converted in the body to a chemical called nitric oxide. This chemical is made naturally by the body and has the effect of making the veins and arteries relax and widen (dilate). When the blood vessels dilate in this way there is more space inside them and hence less resistance. This makes it easier for the heart to pump blood around the body.
Widening the veins also decreases the volume of blood that returns to the heart with each heartbeat. This makes it easier for the heart to pump that blood out again.
As a result of both these actions, the heart does not need as much energy to pump the blood around the body and therefore needs less oxygen.
Isosorbide mononitrate also widens the arteries within the heart itself, which increases the blood and oxygen supply to the heart muscle.
The pain of angina is caused by too little oxygen reaching the heart when its workload increases, such as during exercise. Isosorbide mononitrate improves the oxygen supply to the heart, as well as decreasing the amount of oxygen that the heart needs by making it easier for the heart to pump blood around the body. It can therefore be used to treat angina.
Cibral tablets are taken on a regular basis to help prevent angina attacks. They are usually taken two or three times a day.
Isosorbide mononitrate can also be used in the treatment of heart failure, where the pumping action of the heart has become less effective.
What is it used for?
- Prevention of angina attacks.
-
Heart failure.
Warning!
- This medicine may cause dizziness and so may affect your ability to drive or operate machinery safely. Do not drive or operate machinery until you know how this medicine affects you and you are sure it won't affect your performance.
- Drinking alcohol may enhance some of the side effects of this medicine, such as feeling faint or dizzy.
- With long-term continuous use the body can start to become tolerant to this medicine, which means it may seem less effective. To avoid this problem, it is important that there is a period of time in every 24 hours when the amount of medicine in your blood is allowed to drop. This is acheived by not spacing your doses evenly throughout the day. For example, if you are taking this medicine twice a day, you could take your first tablet in the morning and your second about eight hours later, rather than 12 hours later. Ask your doctor or pharmacist for advice on when is best for you to take your tablets. This will depend on when your angina is usually worse.
- If you think that this medicine has become less effective at preventing your angina attacks you should consult your doctor or pharmacist.
- You should not suddenly stop taking this medicine, as this could cause your angina to get worse. If treatment with this medicine is stopped, this should be done gradually, following the instructions given by your doctor.
Use with caution in
- Severely decreased kidney function.
- Severely decreased liver function.
- People who have recently had a heart attack.
-
Underactive thyroid gland .
- People with low levels of oxygen in their blood, eg due to lung disease.
- Dangerously low body temperature (hypothermia).
- Malnutrition.
Not to be used in
- Allergy to nitrates.
- Low blood pressure (hypotension).
- Low volume of circulating blood (hypovolaemia).
- Inflammation of the sac surrounding the heart that stops the heart from beating properly (constrictive pericarditis).
- Fluid in the sac surrounding the heart that prevents the heart beating properly (cardiac tamponade).
- Narrowing of the main artery coming from the heart (aortic stenosis).
-
Narrowing of one of the valves in the heart.
- Heart disease in which the muscle of the heart grows abnormally (hypertrophic obstructive cardiomyopathy).
- Head injury.
- Bleeding in the brain (cerebral haemorrhage).
- Severe anaemia.
-
Closed angle glaucoma.
- This medicine is not recommended for use in children.
This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- The safety of this medicine for use during pregnancy has not been established. It should only be used during pregnancy if the benefits to the mother outweigh any risks to the developing baby. Seek medical advice from your doctor.
- It is not known if this medicine passes into breast milk. It should only be used by breastfeeding mothers if the benefits to the mother outweigh any risks to the nursing infant. Seek medical advice from your doctor.
Label warnings
- This medication is to be swallowed whole, not chewed.
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