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What does it do?

Isosorbide mononitrate is used to prevent angina pain. It relaxes the blood vessels, allowing more blood to flow to the heart.

Before you start

  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.

How should you take it?

Take isosorbide mononitrate regularly as directed with a glass of water.
Take the slow-release tablets at the same time each day. Swallow the tablet or the divided halves whole. Do not crush or chew.

What if you forget a dose?

Take the missed dose as soon as possible. If it is close to the time for your next dose, skip the missed dose and carry on as normal. Do not take two doses at the same time.

Can you take other medicines?

Some medicines available without a prescription may react with isosorbide mononitrate including:

  • sildenafil (e.g. Viagra®) or similar medicines. DO NOT use these medicines with isosorbide mononitrate. It may cause severe side effects such as a heart attack.

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Change in heartbeat, fainting

Tell your doctor

Headache, flushing

Common when treatment begins - if side effects continue or are severe, tell your doctor.

Stomach upset

Tell your doctor if troublesome

Lightheaded or dizzy after standing up

Stand up slowly. If it continues, or is severe, tell your doctor

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

  • Taking alcohol and isosorbide mononitrate at the same time may increase side-effects.
  • Do not stop taking isosorbide mononitrate without talking to your doctor first.
  • You may see the leftover shell of the tablet in your bowel motions – this is harmless.

This leaflet contains important, but not all, information about this medicine.

Prepared by the MyMedicines Committee at Christchurch Hospital, Te Whatu Ora - Waitaha, New Zealand. March 2023

For more general information about this sheet and its contents, see: What does a My Medicines sheet cover?

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About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at Te Whatu Ora – Waitaha. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed