Common questions about isosorbide mononitrate and isosorbide dinitrate - Brand names: Chemydur XL, Isotard, Monomil XL, Elantan LA, Isoket Retard

Isosorbide mononitrate and isosorbide dinitrate belong to a group of medicines called nitrates. Nitrates are used to treat and prevent angina.

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

Your heart muscles need oxygen in your 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, isosorbide mononitrate and isosorbide dinitrate work 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.

In heart failure, isosorbide mononitrate and isosorbide dinitrate relax the blood vessels, making it easier for your heart to pump blood around your body.

Isosorbide mononitrate and isosorbide dinitrate usually start to work within 1 hour.

Isosorbide mononitrate and isosorbide dinitrate are both generally safe to take for a long time.

Medicines to treat angina attacks

If you have stable angina (the most common type), you'll be given medicine to take when you have an angina attack.

This is called glyceryl trinitrate, or GTN. It comes as a mouth spray or tablets that dissolve under your tongue.

Isosorbide mononitrate and isosorbide dinitrate are not used to treat sudden angina attacks. They work by preventing attacks from happening.

Medicines to prevent angina attacks

If you have angina, to help avoid more attacks you may need to take at least 1 medicine every day for the rest of your life. Some people need to take 2 or more medicines.

Other medicines used to prevent angina attacks are:

• beta blockers – to make the heart beat slower and with less force
• calcium channel blockers – to relax the arteries, increasing blood supply to the heart muscle

If you cannot take either of these medicines, you may be given another medicine such as ivabradine, nicorandil or ranolazine.

Your doctor will help you decide what treatment is best for you.

Tell your doctor that you're taking isosorbide mononitrate or isosorbide dinitrate if you're going to be put to sleep (using general anaesthetic), or you're having any kind of major operation.

Your doctor may advise you to stop taking isosorbide mononitrate or isosorbide dinitrate before surgery. This is because these medicines can lower your blood pressure too much when combined with some anaesthetics.

Isosorbide mononitrate or isosorbide dinitrate are not likely to affect your sex life.

However, do not take medicines for erection problems if you're taking isosorbide mononitrate or isosorbide dinitrate. These include:

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

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.

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

You do not need to avoid playing sports due to taking isosorbide mononitrate or isosorbide dinitrate.

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

It will help if you can:

• 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 tablets or spray before starting exercise, if you need to

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

Isosorbide mononitrate and isosorbide dinitrate will not stop any type of contraception working, including emergency contraception.

However, if you have angina, oral contraceptives such as the combined pill are not recommended because they increase the risk of heart attack and stroke.

Talk to your doctor if you're taking a combined hormonal contraceptive.

Isosorbide mononitrate and isosorbide dinitrate can make some people feel dizzy, sleepy or faint.

If this happens to you, do not drive, ride a bike or use tools or operate 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 isosorbide mononitrate or isosorbide dinitrate. GOV.UK has more information on the law on drugs and driving.

Drinking alcohol can increase the effects of isosorbide mononitrate and isosorbide dinitrate. It can make your blood pressure too low and you may feel dizzy, lightheaded or sleepy.

If your heart failure is directly related to drinking alcohol, you may be advised to stop completely.

Apart from limiting alcohol, you can eat and drink normally while you're taking isosorbide mononitrate or isosorbide dinitrate.

However, if you have angina you may have a higher risk of having a heart attack or stroke.

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

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

Drinking alcohol can increase the effects of isosorbide mononitrate and isosorbide dinitrate. It can make your blood pressure too low and you may feel dizzy, lightheaded or sleepy.

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

To reduce your risk of problems like these, it may help to:

• eat a healthy balanced diet – 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 limit the amount of salt in your diet too
• 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
• quit smoking – smoking increases your heart rate and blood pressure
• 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