Glyceryl Trinitrate (GTN) 500mcg tablets are a medication used to treat symptoms of chest pain (angina). Here?s how you use it:

At the onset of an attack, 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.
If you?re still in pain?5 minutes after your 2nd dose, or if your pain is getting worse, call for emergency medical help.?These could be signs that you may be having a heart attack.

It?s important to sit down before using GTN, as you may experience headaches, flushing, or dizziness soon after use. Always keep your GTN tablets with you and keep a spare one handy.
Please note that this information is a general guide, and you should always follow the instructions provided by your doctor or pharmacist. If you have any concerns or questions about your medication, please consult with a healthcare professional.