About isosorbide dinitrate

Isosorbide dinitrate is for angina. Angina develops if part of your heart muscle does not get as much blood and oxygen as it needs. It is usually caused by narrowing of your coronary arteries due to a build-up of a fatty substance called atheroma. The narrowing makes it more difficult for blood to flow to your heart muscle.

Isosorbide dinitrate works in two ways. It relaxes blood vessels in your body (causing them to widen) and this reduces the strain on your heart, making it easier for your heart to pump blood. It also relaxes and widens the coronary arteries which increases the flow of blood to your heart muscle.

Before taking isosorbide dinitrate

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start isosorbide dinitrate it is important that your doctor or pharmacist knows:

• If you are pregnant, trying for a baby or breast-feeding.
• If you have problems with your liver or kidneys.
• If you have low blood pressure.
• If you have been told by a doctor you have anaemia (low levels of iron in your blood) or hypoxaemia (low levels of oxygen in your blood).
• If you have an underactive thyroid.
• If you have glaucoma (an increased pressure in your eye).
• If you have recently had a head injury or a heart attack.
• If you have ever had an allergic reaction to a medicine.
• If you are taking other medicines, including those available to buy without a prescription, herbal or complementary medicines. It is particularly important that you tell your doctor if you are using any products to help treat erectile dysfunction (such as Viagra®).

How to take isosorbide dinitrate

• Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about the specific type of isosorbide dinitrate tablets you have been given, and a full list of side-effects which you may experience from taking them.
• The short-acting tablets should be taken 3 or 4 times daily, with the last dose being taken no later than 6 pm. Longer-acting tablets are usually taken twice daily, the first dose in the morning and the second dose mid-afternoon. (Longer-acting tablets have 'Retard' in the brand name.) Your doctor or pharmacist will tell you which is the right dose for you, and this will also be printed on the label of the pack to remind you. You can take isosorbide dinitrate tablets before or after meals.
• If you are taking longer-acting tablets, you should swallow them whole - do not chew, break or crush the tablets. This is because they are specially made to release the medicine they contain in a controlled way.
• Try to take the tablets at the same times each day, as this will help you to remember to take them. If you do forget to take a dose, take it as soon as you remember. If it is almost time to take your next dose, skip the missed dose and take your next dose when it is due. Do not take two doses together to make up for a forgotten dose.

Getting the most from your treatment

• Isosorbide dinitrate tablets are not suitable to take to treat an angina attack as they will take too long to work. Your doctor will also prescribe glyceryl trinitrate (GTN) for you to take if this happens. If after using GTN your pain has not eased within a few minutes, call for an ambulance.
• Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress
• The longer you take isosorbide dinitrate, the more your body can get used to it, which sometimes means it has a lesser effect. Your doctor may advise that you have some time during each day without isosorbide dinitrate to avoid this. This means that the tablets may not be prescribed at equal intervals throughout the day. Follow carefully any instructions you have been given about when to take your doses.
• It is best not to drink alcohol while you are taking isosorbide dinitrate. Alcohol will increase the chance that you experience side-effects, such as feeling dizzy or light-headed. If you do drink alcohol, drink only a little and be aware of its effect on you.
• If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.
• If you buy any medicines, check with a pharmacist that they are suitable for you to take with isosorbide dinitrate.

Can isosorbide dinitrate cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

How to store isosorbide dinitrate

• Keep all medicines out of the reach and sight of children.
• Store in a cool, dry place, away from direct heat and light.

Important information about all medicines