GTN sublingual tablets (glyceryl trinitrate)

How does it work?

GTN sublingual tablets contain the active ingredient glyceryl trinitrate, which is a type of medicine called a nitrate. It is used to help the heart work more easily. (NB. Glyceryl trinitrate is also available without a brand name, ie as the generic medicine.)

Glyceryl trinitrate 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.

Glyceryl trinitrate 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. Glyceryl trinitrate 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.

GTN sublingual tablets should be allowed to dissolve under the tongue. This area of the mouth has a large supply of blood vessels that allows the medicine to be rapidly absorbed. Glyceryl trinitrate taken in this way is used to give rapid relief from the pain of an angina attack. The tablets can also be used to prevent an anticipated attack, for example before exercise or physical effort, emotional stress or exposure to cold.

Glyceryl trinitrate is also available as long-acting tablets, skin patches and ointment that are used regularly each day to help prevent angina attacks. See the factsheets linked at the end of this article for more information.

What is it used for?

Prevention and relief of angina attacks.

Warning!

Follow the instructions you receive with this medicine. Glyceryl trinitrate sublingual tablets should be allowed to dissolve under the tongue - they should not be swallowed like normal tablets.

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. If you do feel dizzy after taking a dose, sit or lie down until the symptoms pass.

Drinking alcohol may enhance some of the side effects of this medicine, such as feeling faint or dizzy.

Short-acting glyceryl trinitrate tablets should be kept in the container they are dispensed in and discarded after eight weeks. The tablets may lose their effectiveness if the container has been open for longer than eight weeks, or if the tablets are transferred to a different container.

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. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

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

Allow medication to dissolve under the tongue. Do not transfer from the original container. Keep tightly closed. Discard eight weeks after opening.

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