Like all medicines, glyceryl trinitrate (GTN) can cause side effects, although not everybody gets them. Side effects often improve as your body gets used to the medicine.
Common side effects
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:
Headaches (very common)
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.
Feeling dizzy, weak, tired or sleepy
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.
Feeling sick (nausea)
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.
Red face (flushing)
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
Serious side effects after taking GTN are rare and happen in less than 1 in 1,000 people.
Immediate action required: Call 999 or go to A&E now if:
- 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)
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to GTN.
Immediate action required: 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.
Other side effects
These are not all the side effects of GTN. For a full list see the leaflet inside your medicine packet.
You can report any suspected side effect using the Yellow Card safety scheme.