Isosorbide mononitrate and isosorbide dinitrate

Isosorbide mononitrate and dinitrate are not suitable for some people. For example, check with your doctor if you've had a heart attack or stroke.

Isosorbide mononitrate and dinitrate come as tablets or capsules that you usually take 1 to 3 times a day. Follow the medicine's instructions.

Common side effects of isosorbide mononitrate and dinitrate include headaches and feeling dizzy. More serious side effects can happen in rare cases.

It can cause problems to take isosorbide mononitrate or dinitrate with some other medicines, such as other medicines that lower your blood pressure.

Most adults aged 18 years old and over can take isosorbide mononitrate or isosorbide dinitrate.

Isosorbide mononitrate and isosorbide dinitrate are not suitable for some people. To make sure they're safe for you, tell your doctor or pharmacist if you have:

• ever had an allergic reaction to isosorbide mononitrate or isosorbide dinitrate or any other medicine
• any other heart problems, including a recent heart attack
• any recent brain or head injuries or problems
• ever had a stroke
• an underactive thyroid (hypothyroidism)
• low blood pressure (hypotension)
• anaemia
• glaucoma

How much isosorbide mononitrate or isosorbide dinitrate you take depends on your symptoms, the brand of medicine and the type of tablets or capsules you're taking.

Dose for angina

The usual dose to prevent angina is:

• isosorbide mononitrate standard tablets – 10mg, taken twice a day, up to a maximum dose of 120mg a day, split into smaller doses
• isosorbide mononitrate slow-release tablets or capsules – 25mg to 60mg, up to a maximum dose of 120mg, taken once a day
• isosorbide dinitrate standard tablets – 30mg to 120mg a day, split into smaller doses
• isosorbide dinitrate slow-release tablets – 40mg, taken once or twice a day, up to a maximum dose of 60mg to 80mg, taken 2 or 3 times a day

Dose for heart failure

The usual dose to treat heart failure is:

• isosorbide mononitrate standard tablets – 10mg to 20mg, taken 2 to 3 times a day, or 40mg, taken twice a day, up to a maximum dose of 120mg daily, split into smaller doses
• isosorbide dinitrate standard tablets – 40mg to 160mg a day, up to a maximum dose of 240mg a day, split into smaller doses

Swallow the tablets or capsules whole with a drink of water. Do not chew or crush them.

You can take tablets or capsules with or without food.

Your doctor may tell you to leave a gap of 4 to 14 hours a day (usually when you're sleeping) where you do not take the tablets or capsules. This is called a "nitrate low" period and is needed to make sure your medicine works properly.

If you take isosorbide mononitrate or dinitrate 2 or 3 times a day, your doctor or pharmacist will explain how to space out your doses.

For example, if you're taking standard tablets twice a day, they may tell you to take 1 dose in the morning at 8am and the second dose in the afternoon at 2pm (leaving a gap of 6 hours between your first and second dose).

There are things you can do to help cope with these common side effects of isosorbide mononitrate or isosorbide dinitrate:

Make sure you rest and drink plenty of water. Paracetamol is safe to take with isosorbide mononitrate and isosorbide dinitrate. Do not drink alcohol, as it could make your headaches worse.

Headaches usually go away after a few days. Talk to your doctor if they do not go away or are severe.

Stop what you're doing and sit or lie down until you feel better. Do not drink alcohol, as it could make you feel worse. Do not drive, ride a bike or use tools or machinery until you feel better.

Avoid rich, greasy or spicy foods, as these could make you feel worse. Stick to small, simple snacks or meals if you're hungry. It might help to take isosorbide mononitrate or isosorbide dinitrate after meals.

Try to cut down on coffee, tea and alcohol because they can make flushing worse. It might help to keep the room cool and use a fan. You could also spray your face with cool water or sip non-alcoholic cold or iced drinks.

Talk to your doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.

Isosorbide mononitrate and isosorbide dinitrate can be taken in pregnancy.

However, if you're pregnant or trying for a baby then you should be seen as soon as possible by a pregnancy specialist (obstetrician) and a heart specialist (cardiologist), so your heart health and medicine can be reviewed.

Keep taking your medicine until you've had your review.

If your doctor, midwife or health visitor says your baby is healthy, you may be able to take isosorbide mononitrate or isosorbide dinitrate while you're breastfeeding. Talk to your doctor or pharmacist first, and they'll help you to decide.

It's not known how much isosorbide mononitrate or isosorbide dinitrate gets into breast milk, but it's likely to be low levels. It's unlikely to cause any side effects in your baby.

It's important that you keep taking your medicine to keep you well. Breastfeeding will also benefit both you and your baby.

Talk to your health visitor, midwife, pharmacist or doctor if you have any concerns about your baby. This includes if they're:

• not feeding as well as usual or not putting on weight as you would expect
• unusually sleepy
• being irritable

Some medicines can affect the way isosorbide mononitrate and isosorbide dinitrate work.

If you take other medicines that lower blood pressure with isosorbide mononitrate or isosorbide dinitrate, it can sometimes lower your blood pressure too much. This might make you feel dizzy or faint.

Tell your doctor if this happens to you. They may need to change your dose.

Check with a pharmacist or your doctor before starting to take isosorbide mononitrate or isosorbide dinitrate if you're taking:

• medicines for erection problems including sildenafil, avanafil, tadalafil or vardenafil
• riociguat, used to treat pulmonary hypertension
• medicines for high blood pressure or heart problems
• medicines for depression or other mental health conditions
• medicines for migraine that contain ergotamine such as Migril
• sapropterin, a medicine for phenylketonuria (PKU)

Taking isosorbide mononitrate or isosorbide dinitrate with painkillers

Paracetamol is safe to take with isosorbide mononitrate or isosorbide dinitrate.

Do not take non-steroidal anti-inflammatory drugs (NSAIDs) regularly, such as ibuprofen, aspirin and naproxen (unless it's prescribed by your doctor). These may make your angina or heart failure worse.

Talk to your pharmacist if you need a painkiller stronger than paracetamol.