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Nitrate medicines include glyceryl trinitrate (GTN), isosorbide dinitrate and isosorbide mononitrate. Each has various brand names. Nitrate drugs do not alter the underlying cause of angina. (Angina is usually caused by narrowing of the heart arteries due to a build-up of a fatty substance called atheroma. See the separate leaflet called Angina.) However, nitrate medicines are good at easing and preventing angina pains.

Nitrates work by relaxing the walls of blood vessels, which makes them slightly wider. By relaxing the blood vessels on the surface of the heart, the heart can get more blood flow and oxygen. That helps to treat angina, which is caused by not enough blood flow getting to the heart.

Nitrates also relax other blood vessels in the body, which takes the strain off the heart a little.

Short-acting nitrate preparations

Long-acting nitrate preparations

If you have frequent angina pains, long acting nitrate preparations help to prevent the pains from developing.

A long-acting preparation takes longer to start working, so is not much use for immediate pain relief. But, it works for much longer after each dose than a short-acting preparation (which loses its effect after 20 minutes or so).

Common side-effects include:

  • A throbbing headache.
  • A flushed face.
  • Dizziness.
  • Lightheadedness (from the nitrate causing low blood pressure).
  • Feeling slightly nauseous.
  • With the spray under the tongue: a slight burning or tingling sensation under the tongue.

Thankfully these side-effects are unpleasant but not serious. Often they get better once you've been using the medicine for a few weeks.

  • Nitrates interfere with some other medicines, which may cause problems. In particular, you should not take sildenafil (Viagra®) or similar medicines used for erectile dysfunction (impotence) if you are taking a nitrate. This is because the combination of the medicines could make your blood pressure go far too low, which can be dangerous.

Although they help with the symptoms of chest pain from the blood vessels getting furred up, they don't change the underlying reason for the chest pains. So although they can make you feel better, they don't prevent heart attacks.

If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at the following web address:

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products may have caused.

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Further reading and references