Glyceryl trinitrate (GTN)

What it is used for

• Relieving angina attacks, or preventing one before exercise (spray or tablets)
• Preventing angina (patches)
• Anal fissure (ointment)

Read our guides:

• Coronary heart disease

Off-label uses

Doctors sometimes prescribe a medicine for a condition it is not officially licensed for. This is called off-label use. It is legal and common when there is good evidence it helps, and your doctor should explain why they are suggesting it.

Glyceryl trinitrate (GTN) is not commonly used off-label.

How it works

GTN releases nitric oxide, which relaxes and widens blood vessels. This lowers the work the heart has to do and improves blood flow to the heart muscle, easing chest pain.

Side effects

Like all medicines, Glyceryl trinitrate (GTN) can cause side effects, although not everyone gets them. Many are mild and ease after the first few weeks.

Common side effects

• headache
• flushing
• feeling dizzy or light-headed when standing up

Tell your doctor or pharmacist if these bother you or do not go away.

Serious side effects

These are rare. Call 111 or contact your doctor straight away if you get:

• fainting
• chest pain that does not go away after 2 doses

Call 999 if you have signs of a serious allergic reaction, such as swelling of your lips, mouth, throat or tongue, or trouble breathing.

You can report any side effect to the Yellow Card scheme, run by the medicines regulator.

Stopping and withdrawal

Important safety information

• Sit down before using it, as it can make you feel faint.
• If chest pain has not gone 5 minutes after the second dose, call 999.
• Never take it with medicines for erection problems such as sildenafil, as blood pressure can fall dangerously.

Questions about your medicine?

A pharmacist can answer questions about your medicines for free, without an appointment. You can also ask your GP for a medication review. Check if you can get free prescriptions.