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warfarin and tramadol

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Taking warfarin and tramadol together can cause harmful drug interactions, which can raise the International Normalised Ratio (INR), and result in severe bruising and bleeding, which in some patients could be fatal.

Advice for healthcare professionals:

  • warfarin is a coumarin-derived vitamin K antagonist which has a low therapeutic index, so continue to exercise caution when co-prescribing warfarin with other drugs, to minimise the risk of drug interactions
  • ask patients about all the medicines that they are currently taking
  • be aware of the risk of increased INR when warfarin and tramadol are used together, with a risk of major bruising and bleeding which could be life-threatening
  • consult the product information of any new concomitant therapy for specific guidance on use with warfarin and consider whether warfarin dose adjustment is required
  • consider whether additional monitoring of INR is required when starting tramadol or another concomitant medicine
  • ensure patients are aware of the need to seek medical treatment should they notice the signs of a major bleeding event
  • caution should also be taken if tramadol is co-prescribed with other coumarin-derived anticoagulants such as acenocoumarol
  • report suspected adverse drug reactions to the Yellow Card scheme


  • Drug Safety Update volume 17, issue 11: June 2024: 2

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