Glyceryl trinitrate (GTN) is prescribed for chest pain associated with angina. Tablet and spray formulations are referred to as short-acting preparations. This is because the effect of the medicine lasts for around 20-30 minutes. They are used to provide rapid relief from the pain as and when it happens. They can also be used for when the pain is expected to happen, such as before exercise that is likely to cause chest pain (for example, before climbing stairs).