Take glyceryl trinitrate (GTN) exactly as your doctor or pharmacist tells you to. Always follow the instructions that come with the medicine.
How much GTN you take depends on how bad your angina is and whether you have tablets, spray, or patches.
Sometimes patches are not enough to prevent all your angina attacks. Your doctor may give you GTN tablets as well.
Stopping chest pain during an angina attack
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.
Immediate action required: Call 999 if:
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.
Preventing chest pain before exercise or physical effort
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.
Dose for preventing chest pain caused by angina with a daily patch
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.
Dose for treating anal fissures
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.
How to take GTN tablets
- Sit down.
- Put a tablet under your tongue and close your mouth.
- Allow the tablet to dissolve slowly – do not suck, chew or swallow it.
- Close the container – this is important, so your tablets do not lose their strength.
- 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.
How to use GTN spray
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.
- Sit down.
- If you have not used your spray for over a week, do 1 spray into the air before you use it.
- Hold the nozzle in front of your mouth, with your finger on the button, and take a deep breath.
- Open your mouth and lift your tongue up.
- Spray the GTN under your tongue by pressing once firmly. Do not breathe in while you spray.
- Close your mouth immediately.
- Breathe through your nose keeping your mouth closed.
- 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.
How to put on a GTN patch
- Sit down.
- 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.
- Wash the area of skin and dry it completely. Do not use talcum powder or anything else on your skin.
- Open the GTN packet with your fingers – do not use scissors because you might cut the patch.
- 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.
- Put the sticky side of the patch on the clean skin. Press it down firmly and count to 5.
- 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.
How to use rectal ointment
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.
Changes to your dose
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.
How long to take it for
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 it
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 too much
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.
Immediate action required: Call 999 if:
- 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
Urgent advice: Contact 111 now if:
- you take or use more than your prescribed dose of GTN spray, tablets, patches or ointment and you feel unwell
Go to 111.nhs.uk or call 111.
If you need to go to A&E, do not drive yourself. Get someone else to drive you or call an ambulance.
Take the GTN packet, or the leaflet inside it, plus any remaining medicine with you.