What is aspirin?

Aspirin is an anti-platelet drug often prescribed for people with MPNs. Aspirin is classified as a non-steroidal anti-inflammatory (NSAID) drug. This means that it reduces inflammation but does not contain steroids. It is prescribed at a dose of 100 mg daily for most patients with MPNs in Australia.

How does aspirin work?

Aspirin helps to prevent the development of thrombosis (blood clots) by reducing the ‘stickiness’ of platelets.

How can taking aspirin help me?

People with MPNs are at increased risk of developing a thrombosis (blood clots) in their arteries (e.g. stroke or heart attack) or in their veins (e.g. deep vein thrombosis or pulmonary emboli). This is due to an increase in the number of blood cells and an increase in the tendency of these cells to stick both to each other and to the blood vessel wall. Aspirin reduces the stickiness of platelets, making them less likely to stick to each other and the blood vessel wall. It does not alter the number of platelets or other blood cells.

Recommended dosage

Your haematologist will advise you how much and how often to take aspirin.
For some low risk ET patients, your haematologist will determine whether or not aspirin is appropriate for you.

The most common dose prescribed in Australia is 100 mg once daily but occasionally a higher or lower dose may be recommended by your doctor. Regularly missing doses stops the drug’s effect and causes the platelets to become sticky again, so it is important to maintain your regular dose.

Do not break, crush or chew the tablets.

Take them with a full glass of water.

Follow the directions on the package or prescription label carefully. Ask your doctor or pharmacist to explain any part of the instructions that you do not understand.

Do not take more or less than directed.

Are there any side effects?


Approximately 1–10% of people taking aspirin may experience some of these side-effects:

  • Indigestion or stomach discomfort
  • Gastrointestinal bleeding
  • Other haemorrhage (bleeding) or easy bruising


Less than 0.1% of people taking aspirin may experience some of these side-effects:

  • Kidney or liver abnormalities
  • Allergic reactions (swelling of the face, lips or tongue; asthma; skin itching)
  • Nausea and vomiting
  • Reye’s Syndrome (children)

Frequently asked questions

What if I have other medical conditions?

Please inform your doctor if you have any of the following conditions:

  • Asthma
  • Gastric or duodenal ulcers
  • Previous bleeding problems
  • Acquired von Willebrand syndrome
  • Uncontrollable hypertension
  • Liver problems
  • Kidney problems

Please also inform your doctor if you are pregnant or currently breastfeeding.

Interactions with other medications

Always provide the names of medicines prescribed for you as well as any vitamins, herbal supplements or remedies to the haematologists, GPs, and pharmacists who are treating you. It can be very helpful to carry a list of the names and dosages of all your medicines to show to your doctor at appointments.

Aspirin can interact with some other drugs, and it can also interact with alcohol. Please inform your doctor if you consume alcoholic drinks and if you take any of the medications listed below:

  • Clopidogrel or other anti-platelet (blood-thinning) medications
  • Heparin
  • Other NSAIDs (eg Naprosyn or Voltaren)
  • Warfarin
  • NOACs (eg apixaban, rivaroxaban, dabigatran)

Some supplements have an antiplatelet (blood-thinning) effect when taken in large doses, including fish oil, vitamin E and turmeric. Please discuss the use of these supplements with your doctor.

What if I need to have a medical procedure?

It is usually but not always advisable to stop taking aspirin for seven to ten days prior to any invasive surgical procedures to prevent bleeding. Please ensure you discuss whether this is necessary with the doctor or dentist performing the procedure and your haematologist.

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