Glyceryl trinitrate (GTN)

Glyceryl trinitrate, or GTN, is a type of medicine called a nitrate. It's used to prevent and treat chest pain caused by angina.

It can help stop chest pain if an angina attack has already started. It can also help to prevent the chest pain starting.

It comes as tablets or as a spray that you put under your tongue. It also comes as patches that you put on your skin.

Sometimes GTN patches are used in hospital to make your veins easier to see if you need to have a drip (infusion).

GTN is also available as a rectal ointment used to treat tears in the skin around your bottom (anal fissures).

GTN rectal ointment is available on prescription. You can buy GTN tablets, spray and patches from a pharmacy.

You use glyceryl trinitrate (GTN) tablets and spray under your tongue. The medicine is absorbed into your body very quickly this way, so you can take it for fast relief of chest pain caused by angina.

It's a good idea to learn how to take your GTN tablets and spray as soon as you get them. You might need to take them in a hurry if you get an angina attack.

Keep your tablets or spray with you all the time, so you can take them if you get chest pain.

Do not use more than 2 doses during an angina attack. 1 dose is either 1 tablet or 1 to 2 sprays.

Dose for tablets

Put 1 tablet under your tongue as soon as possible. If you're still in pain after 5 minutes you can have a second dose by putting 1 more tablet under your tongue.

Dose for spray

Use 1 or 2 sprays under your tongue. If you're still in pain after 5 minutes you can have a second dose of 1 or 2 sprays under your tongue.

you've taken 2 doses of GTN and:

• you're still in pain 5 minutes after your 2nd dose
• your pain is getting worse
• you feel unwell

These are signs that you may be having a heart attack.

Do not drive yourself to A&E.

The person you speak to at 999 will give you advice about what to do.

Dose for tablets

Put 1 tablet under your tongue before you start your activity. The tablets usually take 1 to 3 minutes to work.

Dose for spray

Use 1 or 2 sprays under your tongue before you start your activity. The spray usually takes 1 to 3 minutes to work.

Usually you put on 1 patch in the morning and take it off before you go to bed at night. Put on a new patch each morning.

It's best to have 8 to 12 hours without a patch otherwise the GTN can stop working over time.

Usually 1 patch a day is enough. If this does not work, your doctor might increase your dose, or tell you to keep the patch on for longer.

Do not stop using the patches suddenly without talking to your doctor first.

The usual dose is approximately 375mg of ointment applied to the anal canal twice a day.

Use the 2.5cm dosing line on the outside of the carton to measure the right amount of ointment.

1. Sit down.
2. Put a tablet under your tongue and close your mouth.
3. Allow the tablet to dissolve slowly – do not suck, chew or swallow it.
4. Close the container – this is important, so your tablets do not lose their strength.
5. Rest for a while, then stand up slowly.

Do not use tablets from a bottle that was first opened more than 8 weeks ago.

It's a good idea to have a spare, unopened bottle of tablets. It's important to not run out.

Before using the spray for the first time, check it's working. Press the button on the nozzle at the top of the bottle a few times until a fine mist comes out. Do a test spray onto a tissue so you know how it works.

1. Sit down.
2. If you have not used your spray for over a week, do 1 spray into the air before you use it.
3. Hold the nozzle in front of your mouth, with your finger on the button, and take a deep breath.
4. Open your mouth and lift your tongue up.
5. Spray the GTN under your tongue by pressing once firmly. Do not breathe in while you spray.
6. Close your mouth immediately.
7. Breathe through your nose keeping your mouth closed.
8. Rest for a while before you stand up slowly.

It's a good idea to have a spare spray. It's difficult to tell how much is left in a bottle and it's important to not run out.

1. Sit down.
2. Decide where to put your patch – choose an area of skin with no hair, or very little hair, so the patch sticks well. Good places are the side of your chest, upper abdomen, upper arm, shoulder or thigh. Put your patches in a different place each day of the week and wait several days before using the same place again.
3. Wash the area of skin and dry it completely. Do not use talcum powder or anything else on your skin.
4. Open the GTN packet with your fingers – do not use scissors because you might cut the patch.
5. Remove the patch from the packet. Peel the plastic backing off the patch and throw it away. Do not touch the sticky surface of the patch with your fingers.
6. Put the sticky side of the patch on the clean skin. Press it down firmly and count to 5.
7. Rub your finger round the edge of the patch to make sure no air or water can get in.

If you have put your patch on properly, you can have a warm (not too hot) bath or shower or go swimming while the patch is on.

If you have been prescribed rectal ointment for an anal fissure, ask your doctor or pharmacist about the best way to put it on or follow the instructions in the leaflet.

You may need to reduce your dose if you get too many side effects or if you start taking other medicines. Your doctor will discuss this with you.

You may need a stronger dose if GTN stops working as well as it used to. This sometimes happens. Tell your doctor if you notice that GTN is not working as well as usual.

If you have angina, you'll usually take GTN for a long time, possibly for the rest of your life.

Talk to your doctor if you want to stop taking GTN.

If you've been taking GTN regularly and you stop taking it, your angina may get worse. This may increase your risk of a heart attack or stroke.

If you're bothered by side effects, speak to your doctor. They may be able to change your dose or prescribe a different medicine instead.

If you're using GTN for an anal fissure, you'll take it for up to 8 weeks.

If you forget to take your GTN before exercise, or another activity that could cause an angina attack, take it as soon as you remember. Do not restart the exercise or activity until the GTN has had the usual time to work.

If you forget to put your daily patch on at the usual time, put a new patch on as soon as you remember, unless it's nearly time for your next patch. In this case, skip the missed patch and put on the next one at the usual time.

If you miss a dose of your rectal ointment, use it as soon as possible, unless it's nearly time for your next dose. In this case, leave out the missed dose and apply the next one at the usual time.

Never have an extra dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm or reminder to help you remember. You can also ask a pharmacist for advice on other ways to help you to remember to take your medicine.

If you take more than your prescribed dose of GTN spray, sit down and put your feet up if you feel faint.

If you take more than your prescribed dose of tablets, remove any tablets that are left undissolved in your mouth.

If you use more than your prescribed number of patches, remove them.

If you use more than your prescribed dose of ointment, wash it off.

You might get side effects such as headaches, a fast heartbeat or feeling dizzy.

• you take or use more than your prescribed dose of GTN and your mouth (lips, tongue or gums), face or skin start to look blue or grey – if you have brown or black skin, this may be easier to see on your lips, tongue and gums or around your eyes

• you take or use more than your prescribed dose of GTN spray, tablets, patches or ointment and you feel unwell

Get help from 111 online or call 111

If you need to go to A&E, do not drive. Ask someone to drive you or call 999 and ask for an ambulance.

Bring the GTN packet or leaflet inside it, any remaining medicine, and any other medicines you take.

Most adults aged 18 years old and over can take GTN. It's not used for children.

This medicine is not suitable for some people. To make sure it's safe for you, tell your doctor or pharmacist if you have:

• ever had an allergic reaction to GTN or any other medicine
• any recent brain or head injuries or problems, including bleeding in your brain and raised pressure in your head
• ever had a stroke
• any heart problems (other than angina), including a recent heart attack or heart failure
• low blood pressure (hypotension)
• anaemia
• glaucoma

These common side effects of glyceryl trinitrate (GTN) happen in more than 1 in 100 people, but some are less likely if you're using skin patches. There are things you can do to help cope with them:

Make sure you rest and drink plenty of fluids. Do not drink too much alcohol.

Ask your pharmacist to recommend a painkiller. Paracetamol is safe to take with GTN.

Headaches usually go away after a few days if you use GTN regularly. Talk to your doctor if they last longer than a week or are severe.

If you're using GTN rectal ointment your doctor or pharmacist may suggest reducing the amount you use for a few days.

Stop what you're doing and sit or lie down until you feel better. Do not drive, cycle or use tools or machinery if you're feeling dizzy, weak or tired.

Do not drink alcohol as it could make you feel worse.

This usually goes away on its own, but it might help to take sips of a cold drink or peppermint tea. This will also stop you getting dehydrated.

Avoid rich, greasy or spicy foods, as these could make you feel worse. Stick to small, simple snacks or meals if you are hungry.

Try cutting down on coffee, tea and alcohol.

It might help to keep the room cool and use a fan. You could also spray your face with cool water or sip cold or iced drinks.

The flushing should go away after a couple of hours if you have used GTN only once, or after a few days if you use GTN every day.

Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.

Serious side effects after taking GTN are rare and happen in less than 1 in 1,000 people.

• you're having breathing difficulties that are new or worse than usual
• your lips, tongue, face or skin suddenly turn blue or grey, or if you have darker skin and your gums and round the eyes turn blue or grey – these are signs of a problem with the oxygen levels in your blood
• your heart starts beating much faster or slower than usual
• you get chest pain that is different or worse than your usual angina pain
• you have fainted (lose consciousness)

Do not drive to A&E. Ask someone to drive you or call 999 and ask for an ambulance.

Bring all the medicines you take with you.

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to GTN.

Call 999 now if:

• your lips, mouth, throat or tongue suddenly become swollen
• you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
• your throat feels tight or you're struggling to swallow
• your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
• you suddenly become very confused, drowsy or dizzy
• someone faints and cannot be woken up
• a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of GTN. For a full list see the leaflet inside your medicine packet.

Glyceryl trinitrate is not harmful if used in pregnancy. However, you will not usually need GTN if you're pregnant.

If you're taking GTN for angina, you should be reviewed by a pregnancy specialist (obstetrician) and a heart specialist (cardiologist). You can continue to take GTN until you've had your review.

If you're using GTN to treat anal fissures, speak to your doctor, who may suggest an alternative medicine.

If your doctor, health visitor or midwife says your baby is healthy, you can take or use GTN if you're breastfeeding.

Although there's not much information about using GTN rectal ointment while breastfeeding, it's not thought to cause any side effects in babies. Wash your hands thoroughly after applying the ointment and before picking up your baby.

There is no information about using GTN tablets, sprays or patches while breastfeeding. It is not known how much GTN gets into breast milk, but it's likely to be a very small amount, and too low to cause any side effects.

Talk to your health visitor, midwife, doctor or pharmacist as soon as possible if you have any concerns, including if your baby:

• is not feeding as well as usual
• seems unusually sleepy or pale
• has a red face (flushing) immediately after breastfeeding

There's no evidence that glyceryl trinitrate affects fertility in either men or women.

Speak to a pharmacist or your doctor if you're trying to get pregnant.

Tell your doctor if you're:

• trying to get pregnant
• pregnant
• breastfeeding

There are some medicines that may affect how glyceryl trinitrate (GTN) works.

If you take other medicines that lower blood pressure with GTN, it can sometimes lower your blood pressure too much. This might make you feel dizzy or faint.

Tell your doctor if this happens to you. They may need to change your dose.

Tell your doctor or pharmacist if you're taking:

• medicines for erection problems such as alprostadil, avanafil, sildenafil (Viagra), tadalafil (Cialis) or vardenafil
• anticoagulant medicine to prevent blood clots such as heparin
• medicines for depression or other mental health conditions
• medicines for high blood pressure or heart problems
• medicines for migraine that contain ergot alkaloids or ergotamine
• medicines for Parkinson's disease such as apomorphine

If you take GTN tablets, tell a doctor or pharmacist if you take any medicines that make your mouth dry (including some antidepressants, cold medicines or medicines for urinary incontinence). This is because a dry mouth can reduce how well GTN tablets work, so GTN spray may be better for you.

Paracetamol is safe to take with GTN.

Do not take non-steroidal anti-inflammatory drugs (NSAIDs) regularly, such as ibuprofen, aspirin or naproxen. These may make your angina worse.

Talk to your pharmacist if you need a painkiller stronger than paracetamol.

There's not enough information to say that complementary medicines and herbal remedies are safe to take with GTN. They're not tested in the same way as pharmacy and prescription medicines. They're generally not tested for the effect they have on other medicines.

Tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.