Glyceryl trinitrate (GTN) belongs to a group of medicines known as nitrates. GTN sublingual is used to relieve sudden angina (chest pain) attack.
This medicine may also be used to help prevent chest pain from developing.
GTN cannot cure your chest pain; it can only temporarily relieve your discomfort. If your doctor has given you other heart medicines, make sure you take them as directed.
Take GTN exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
GTN is available as a sublingual tablet or as a spray.
It is recommended to take/use this medicine while you are on a sitting position.
If you are taking the tablet, it must be placed under your tongue to be effective. Allow it to dissolve. GTN is absorbed into your body through the lining of your mouth. Do not swallow, chew or crush the tablet.
To use GTN spray, follow these steps:
- If you are using the spray for the first time, remove the cap and press the pump a few times until you produce a fine mist.
- Hold the spray upright and place the spray outlet close to your mouth.
- Press down the pump button firmly and release the spray directing under your tongue.
- Release the pump button and close your mouth immediately after each dose. Hold your breath for a moment to avoid breathing in the spray. Avoid swallowing and do not spit out or rinse your mouth for 5 to 10 minutes after using this medicine.
- Replace the cap.
If you are not sure how to use the spray, ask your pharmacist.
The dose of this medicine will be discussed by your doctor. Your doctor will advise you on the guidelines on how and when you should take this medicine.
Always carry your GTN as you will need it during a sudden angina attack or to prevent chest pain from developing due to certain physical activities or emotional stress.
Alert your doctor if you have the following conditions:
- recent heart attack, stroke, or heart disorders e.g. inflammation of the heart, narrowing of the heart valves, build-up of fluid around the heart
- increased pressure in the head, brain/head trauma or injury
- severe anaemia (low red blood cell count)
- severe low blood pressure
- glaucoma (increased pressure in the eye)
- swelling of the lungs
as GTN may not be suitable for you.
Do not use GTN with medicines used to treat impotence and medicines used to manage high blood pressure in the arteries of the lungs. Please see the section “Can I take this with other medicines?” below for more information.
Inform your doctor if you have the following:
- liver disease
- kidney disease
- thyroid disease e.g. underactive thyroid gland
- poor nutrition due to unbalanced diet or digestion problems
Let your doctor know if you are pregnant or breastfeeding.
Be sure to check with your doctor or pharmacist before giving this medicine to the elderly. Elderly may be more sensitive to the side effects.
Make sure you see your doctor regularly for follow-ups. Let your doctor know if your chest pain seems worse or if GTN does not seem to help.
GTN sublingual may cause dizziness. If affected, do not drive or take part in any activity in which you need to be alert.
Other side effects include any of the following: headache, nausea, generalised weakness or lack of energy, facial flushing.
This medicine may cause your blood pressure to fall suddenly when you get up from a sitting or lying down position and you may feel giddy. To minimise this problem, stand up slowly.
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
DO NOT take GTN with the following medicines:
- medicines used to treat impotence e.g. sildenafil, tadalafil, vardenafil
- riociguat (medicines used to manage high blood pressure in the arteries of the lungs)
Inform your doctor and pharmacist if you are taking any of these medicines:
- medicines for high blood pressure e.g. enalapril, metoprolol, amlodipine
- heparin (a blood-thinning medicine)
- apomorphine (medicine for Parkinson's disease)
- dihydroergotamine (medicine for migraine)
This list does not include all medicines that may interact with GTN.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements and medicines that you buy without a prescription.
Store in a cool, dry place away from the reach of children.
Medicines must not be used past the expiry date.
GTN tablets are very sensitive to heat and moisture. When you carry them around with you, do not keep them too near your body as your body heat may cause the medicine to become ineffective. It is better to put them in your bag. Do not stuff cotton wool or tissue paper into the bottle.
Keep your GTN tablets in the original bottle and do not transfer to any other container. Keep the bottle tightly closed. Discard 8 weeks after opening, whether or not you have finished the tablets in the bottle. Write the opening date on the bottle so that you can easily keep track of the time.