The Aword

  • Increase font size
  • Default font size
  • Decrease font size

Haematological (Blood) Adverse Effects

E-mail Print PDF


Most NSAIDs affect platelet aggregation and hence the clotting of the blood. Aspirin has an irreversible effect on platelets, which is why it is used prophylactically to prevent strokes and heart attacks in those at risk.

One dose may increase the bleeding time for up to 7 days.  Other NSAIDs exert a reversible effect which only lasts until the drug has been eliminated from the body.

This is of particular relevance clinically in patients requiring surgery. Aspirin must be discontinued at least a week prior to the planned procedure and other NSAIDs must be stopped for a period approximating to 4-5 half-lives of the relevant drug.

Anaemia is rarely of a severity to necessitate discontinuation of the drug. Of course, if there is evidence of anaemia or a drop in haemoglobin, then this should raise suspicion of an occult GI bleed.

Patients should be instructed to be vigilant for signs such as easy bruising, bleeding gums, black tarry stools and severe headaches.