Common questions about glyceryl trinitrate (GTN) - Brand names: Rectogesic, Minitran, Glytrin

Glyceryl trinitrate, or GTN, is a type of medicine called a nitrate. Nitrates are used to treat angina.

Angina is chest pain that happens when not enough blood gets to the muscles of the heart. It usually happens because your arteries have become hardened and narrowed.

Your heart muscles need the oxygen in blood to work. If your heart needs to work harder, during exercise for example, it needs increased blood flow to get more oxygen.

In angina, GTN works by widening blood vessels (veins and arteries). This increases the blood supply to your heart, which gets more oxygen to your heart muscles and this reduces chest pain.

By widening blood vessels GTN also makes it easier for your heart to pump blood around your body, so your heart muscles get more oxygen, reducing the risk of getting chest pain.

There are no issues with taking GTN for a long time. Most people can take it with no problems.

Talk to your doctor if you want to stop taking GTN.

If you've been taking GTN regularly and you stop taking it, your angina may get worse. This may increase your risk of a heart attack or stroke.

If you're taking GTN and are bothered by side effects, speak to your doctor. They may be able to change your dose or prescribe a different medicine instead.

GTN is the only medicine available for fast relief of angina symptoms and to prevent pain before exercise or physical effort.

There are other medicines that can be taken regularly to prevent angina attacks, including:

• long-acting nitrates, such as isosorbide mononitrate
• beta blockers such as atenolol
• calcium channel blockers such as verapamil or diltiazem
• medicines such as ranolazine, nicorandil or ivabradine

Your doctor will advise you on which is the best medicine for you.

GTN tablets go out of date (expire) 8 weeks after the bottle is opened. This is because the active ingredient can evaporate, which means the tablets will not work properly after that time.

To make sure your tablets do not lose their strength before 8 weeks:

• keep them in the bottle they came in
• close the lid tightly after you have taken each tablet out
• do not put anything else inside your tablet bottle

It may help to make a note of the date you first opened the bottle. You could write this on the bottle as long as you do not cover anything else on the label.

Make sure you have a new supply of GTN to use after each pack expires. Always check the expiry date on the pack.

After 8 weeks, if you have any tablets left in the bottle, return that bottle to a pharmacy so they can dispose of it in the right way.

If you're having surgery, let the doctors know that you take GTN. They might ask you to stop taking GTN for a short time before surgery.

This is because some of the medicines used to make you sleep and not feel pain during surgery (anaesthetic) can make the side effects of GTN worse.

You must tell the doctor or nurse if you're wearing a GTN patch if you're going to have certain types of tests and treatments including:

• an MRI scan
• diathermy treatment (treatment using hot wires)
• electrical treatment on your heart

Some people with angina worry that having sex will trigger an angina attack, but the risk of this happening is low. It's as safe as other forms of exercise with similar levels of effort.

If you're worried about having an angina attack during sex:

• keep your GTN nearby, so you can use it quickly if you need to
• think about taking a tablet or using your spray before you have sex, to reduce the risk of an attack

GTN is not likely to affect your sex life in any other way.

Talk to your doctor if you're having problems with your sex life.

You cannot take medicines for erection problems if you're using GTN. These include:

• avanafil
• sildenafil (Viagra)
• tadalafil (Cialis)
• vardenafil

If you've used one of these medicines, do not use or take GTN for at least 24 hours after sildenafil or vardenafil, and at least 48 hours after tadalafil.

If you have an angina attack after using one of these medicines for erection problems, stop sexual activity immediately and rest. Do not use GTN.

It's important to stay active if you have angina.

You might worry that exercising could trigger your symptoms or cause a heart attack, but the risk is low if you:

• build up your activity level gradually and take regular breaks
• keep your GTN tablets or spray with you in case you need them
• use your GTN tablets or spray before starting exercise, if you need to

Talk to your doctor if you're not sure whether it's safe for you to exercise.

GTN does not affect any type of contraception, including the combined pill and emergency contraception.

If you have angina, oral contraceptives are not recommended because they increase the risk of heart attack and stroke.

GTN can make some people feel dizzy, sleepy or faint. If this happens to you, do not drive, ride a bike or use tools or machinery until you feel better.

It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.

Talk to your doctor or pharmacist if you're unsure whether it's safe for you to drive while taking GTN. GOV.UK has more information on the law on drugs and driving.

Alcohol increases the blood pressure lowering effect of GTN, so it can make you feel dizzy, faint or sleepy.

If this happens to you, it's best not to drink alcohol while you're taking or using GTN. If this does not happen to you, it's still better to not drink too much alcohol while you're taking or using GTN.

Apart from avoiding too much alcohol, you can eat and drink normally while you're taking or using GTN, but angina is a warning sign that you're at risk of serious problems such as heart attacks and strokes.

You can help reduce your risk of problems like these by:

• eating a balanced diet
• cutting down on alcohol
• losing weight if you are overweight

Angina is a warning sign that you're at risk of serious problems such as heart attacks and strokes.

If you've been prescribed GTN, you can also boost your health by making some key lifestyle changes.

• Eat well – aim to eat a diet that includes plenty of fruit and vegetables, wholegrains, fat-free or low-fat dairy products, and lean proteins. This should help you to stay healthy or lose weight, which reduces your risk of heart attacks and strokes. It's a good idea to follow these tips for a lower salt diet. Aim for no more than 6g of salt a day.
• Cut down on alcohol – drinking too much alcohol is not good for the health of your heart. Try to keep to the recommended guidelines of no more than 14 units of alcohol each week, spread across 3 or more days. A medium glass of wine (175ml) is 2 units. A pint of lager or beer is usually 2 to 3 units of alcohol.
• Quit smoking – smoking increases your heart rate and blood pressure. Quitting smoking will cut your risk of heart attack and stroke. Try to avoid secondhand smoke too.
• Exercise – regular exercise keeps your heart and blood vessels in good condition. It does not need to be too energetic – walking every day will help. Use your GTN tablets or spray before exercise if you need to.