Antiplatelets, aspirin, low dose

Page last reviewed: 13/07/2011

Aspirin is an antiplatelet medicine, which means it reduces the risk of clots forming in your blood.

Low-dose aspirin (usually 75mg a day) may be given to you if you have had:

  • a heart attack
  • a stroke
  • acute coronary syndrome (minor heart attack or unstable angina) 
  • atrial fibrillation
  • a coronary artery bypass operation

It may also be given to you if you are considered to be at risk of having a heart attack or stroke. You may be considered to be at risk if you:

  • have high cholesterol
  • have high blood pressure
  • have diabetes
  • smoke

You may also be advised to take low-dose aspirin if you have diabetes and you:

  • have retinopathy (damage to the retina of the eye)
  • have nephropathy (kidney damage)
  • have had diabetes for more than 10 years
  • are over 50 years old
  • are taking medicines for high blood pressure

Treatment with an antiplatelet medicine such as aspirin is usually for life.

Higher doses of aspirin may be given for other conditions, but these pages focus on the use of low-dose aspirin.

Use in children

Aspirin may be given to children under specialist supervision after heart surgery, or to treat children with Kawasaki disease.

Aspirin must not be given to anyone under 16 years old, unless under specialist advice (see Aspirin - considerations for more information).

How it works

Antiplatelet medicines reduce the risk of clots forming in the blood. This reduces your risk of having a stroke or heart attack.

Normally, when there is a cut or break in a small blood vessel, a blood clot forms to plug the hole until the blood vessel heals.

Small cells in the blood called platelets make the blood clot. When a platelet detects a damaged area of a blood vessel, it produces a chemical that attracts other platelets and makes them stick together to form a blood clot.

Aspirin reduces the ability of the platelets to stick together and reduces the risk of clots forming.

Glossary
Bypass
A bypass is when the flow of blood or other fluid is redirected, permanently because of a blockage in the body, or temporarily during an operation.
Cholesterol
Cholesterol is a fatty substance made by the body that lives in blood and tissue. It is used to make bile acid, hormones and vitamin D.
High blood pressure
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90mmHG.
Retina
The retina is the nerve tissue lining the back of the eye, which senses light and colour and sends it to the brain as electrical impulses.

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Page last reviewed: 13/07/2011

When to avoid aspirin

Low-dose aspirin should not be taken if you have:

  • an active (bleeding) peptic ulcer
  • haemophilia or any other bleeding disorder
  • an allergy to aspirin or to non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or diclofenac

Aspirin must not be given to anyone under 16 years old, unless under specialist advice.

Using aspirin with caution

Low-dose aspirin should be taken with caution if you have:

  • asthma
  • uncontrolled high blood pressure
  • had a previous peptic ulcer
  • liver problems
  • kidney problems

Occasionally, some people are advised to stop taking aspirin seven days before a planned operation. This should always be on the advice of your doctor or surgeon.

Pregnancy and breastfeeding

Low-dose aspirin (75mg) may be taken if you are pregnant or breastfeeding, but only on the recommendation of your GP. Aspirin at doses higher than 150mg per day is not recommended during pregnancy or breastfeeding.

Aspirin should be used with caution during the last three months of pregnancy because of the risk of haemorrhage (bleeding).

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Page last reviewed: 13/07/2011

Common side effects

Common side effects of aspirin include:

  • irritation of the stomach or bowel
  • indigestion
  • nausea (feeling sick)

Less common side effects

Less common side effects of aspirin include:

  • worsening of asthma caused by narrowing of airways
  • allergic reactions
  • vomiting
  • inflammation (swelling) of the stomach
  • bleeding in the stomach
  • bruising

Very rare side effects

A possible side effect of taking low-dose aspirin is haemorrhagic stroke (bleeding in the brain), but this is very rare.

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Page last reviewed: 13/07/2011

When two or more medicines are taken at the same time, the effects of one of the medicines can be altered by the other. This is known as a drug-drug interaction. Aspirin can interact with other medicines.

Some of the more common interactions are listed below. However, this is not a complete list.

If you want to check that your medicines are safe to take with aspirin, ask your doctor or pharmacist, or read the patient information leaflet that comes with your medicine.

Anti-inflammatory painkillers

Aspirin should not be taken with anti-inflammatory painkillers such as diclofenac, ibuprofen, indometacin or naproxen, as this increases the risk of bleeding in the stomach.

Methotrexate

Aspirin can reduce the body's ability to remove methotrexate, and can therefore increase your risk of serious side effects from this drug.

SSRI antidepressants

Taking aspirin with SSRI antidepressants such as citalopram, fluoxetine, paroxetine, sertraline or venlafaxine may increase your risk of bleeding.

Warfarin

Warfarin is an anticoagulant that prevents your blood from clotting. Aspirin taken with warfarin can increase your risk of bleeding. However, there are some situations where you may be advised by your doctor to take aspirin and warfarin together.

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Interactions with food and alcohol

There are no known interactions between aspirin and alcohol or food.

However, it is a good idea to take aspirin with or after food, to help reduce any irritation to the stomach.

Page last reviewed: 13/07/2011

Missed doses

If you forget to take your dose of aspirin, take that dose as soon as you remember and then continue to take your course of aspirin as normal.

However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

If you have to take two doses closer together than normal, there is an increased risk of side effects.

You can also check the patient information leaflet that comes with your medicine, as this will give you advice about what to do.

Extra doses

If you accidentally take an extra dose of low-dose aspirin, it is unlikely to cause you harm as larger doses of aspirin are given safely for other conditions.

However, if you feel unwell or are concerned speak to your GP or pharmacist or call your GP Out of Hours Service.

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Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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