• Carry glyceryl trinitrate (GTN) spray or tablets with you all the time.
  • Your pain should ease within a few minutes after using GTN; if not, call for an ambulance.
  • The most common side-effect is a headache. This should soon pass.

About glyceryl trinitrate

Type of medicine Nitrate
Used for Angina
Heart failure
Also called GTN, Coro-Nitro®, Deponit®, Glytrin®, Minitran®, Nitro-Dur®, Nitrolingual®, Nitromin®, Percutol®, Transiderm-Nitro®
Available as Spray, sublingual tablets (for under the tongue), ointment, patches and injection

Glyceryl trinitrate (GTN) is used for angina. A short-acting preparation (such as a spray or a tablet) is taken to ease angina pain when it happens. Some people take a tablet or a spray before certain types of exercise if they know a pain is likely to develop. Patches are longer-acting and are used regularly to prevent angina pain from occurring.

Angina pain develops if part of your heart muscle does not get as much blood and oxygen as it needs. It is usually caused by narrowing of your coronary arteries due to a build-up of a fatty substance called atheroma. The narrowing makes it more difficult for blood to flow to your heart muscle. GTN works in two ways. It relaxes blood vessels in your body (causing them to widen) and this reduces the strain on your heart, making it easier for your heart to pump blood. It also relaxes and widens the coronary arteries which increases the flow of blood to your heart muscle.

(There is also a rectal ointment of GTN available, but this is used for a completely different condition. See separate medicine leaflet called Glyceryl trinitrate rectal ointment which gives more information about this.)

Before starting glyceryl trinitrate

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

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you have problems with your liver or kidneys.
  • If you have low blood pressure.
  • If you have been told by a doctor you have anaemia (low levels of iron in your blood) or hypoxaemia (low levels of oxygen in your blood).
  • If you have an underactive thyroid.
  • If you have glaucoma (an increased pressure in your eye).
  • If you have recently had a head injury or a heart attack.
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking other medicines, including those available to buy without a prescription, herbal or complementary medicines. It is particularly important that you tell your doctor if you are using any products to help treat erectile dysfunction (such as Viagra®).

How to take glyceryl trinitrate

  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about the preparation you have been given and a full list of side-effects which you may experience.
  • Follow the instructions your doctor has given you. Your dose will be on the label of the pack to remind you.

Spray: spray one or two sprays under your tongue when a pain develops. Close your mouth immediately after using the spray. Your pain should ease within a minute or so. If the first dose does not work, take a second after five minutes. If the pain continues for 15 minutes despite taking GTN, then call an ambulance.

Sublingual tablets: place one tablet under your tongue when a pain develops and allow it to dissolve. Your pain should ease within a minute or so. If the first dose does not work, take a second tablet after five minutes. If the pain continues for 15 minutes despite taking GTN, then call an ambulance.

Patches: apply one patch every 24 hours. It is usual to apply the patches to your chest or upper arm, but this may vary depending upon which brand of patches you have been given. If you are in any doubt, check the manufacturer's information leaflet from inside the pack. Use a different area of skin each time you apply a patch. When you use GTN all the time, your body becomes used to it and then it has much less of an effect. To overcome this tolerance, your doctor may advise you remove the patch before you go to bed, to leave your blood free of nitrate in the early hours when you are asleep.

Ointment: use 1-2 inches of ointment (using the measure provided) and apply it to your chest, arm, or thigh every 3-4 hours as required. Use a different area of skin each time you apply the ointment.

Getting the most from your treatment

  • Carry your GTN spray or tablets with you so thay you can take a dose when a pain develops. GTN tablets go off after a few weeks so you need to get a fresh supply of tablets every eight weeks and return any unused tablets to your pharmacist. Many people prefer to use a GTN spray which has a much longer shelf life than the tablets.
  • After you have used a spray or a tablet for an angina attack, your pain should ease within a few minutes. If the first dose does not work, take a second. If after a second dose the pain does not ease, call an ambulance straightaway.
  • It is best not to drink alcohol while you are using glyceryl trinitrate. Alcohol will increase the chance that you experience side-effects such as feeling dizzy or light-headed. If you do drink alcohol, drink only a little and be aware of its effect on you.
  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking. GTN patches may need to be removed before some treatments and procedures.
  • If you buy any medicines, check with a pharmacist that they are suitable for you to take with GTN.

Can glyceryl trinitrate cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Common GTN side-effects - these affect around 1 in 10 people who take this medicine What can I do if I experience this?
Headache Ask your doctor or pharmacist to recommend a suitable painkiller
Feeling dizzy or weak Do not drive or use tools or machines
Feeling sick This should soon pass
Flushing If troublesome, speak with your doctor

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

How to store glyceryl trinitrate

  • Store sublingual tablets in their original container. They can be used for up to eight weeks after the container has been opened.
  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.