Paracetamol and Warfarin Interaction

Mechanism and Evidence of Interaction

Paracetamol increases INR in a dose-dependent manner when taken with warfarin, requiring close monitoring of INR during concomitant use, especially when doses exceed 2 g/day 1
The interaction appears to be dose-dependent, with the risk of developing an INR > 6 increasing 10-fold once paracetamol intake exceeds 9.1 grams per week 1
Concomitant paracetamol at doses >2 g/day significantly increases INR by an average of 0.7 by day 3 1

Close monitoring of INR is recommended during the initiation of paracetamol therapy in patients taking warfarin 1
Patients at higher risk of bleeding complications require extra caution when using this combination, according to the American College of Cardiology 2
When warfarin is used with any additional medication that increases bleeding risk, careful monitoring is essential, as stated by the American Heart Association 3
For patients requiring warfarin plus antiplatelet therapy, the addition of paracetamol represents a further increase in bleeding risk 4

Overlooking the cumulative dose of paracetamol from multiple products can lead to significant interactions with warfarin 1