Drug interactions
paracetamol + warfarin
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Paracetamol can increase INR and bleeding risk in warfarin-treated patients, especially with ≥2–3 g/day for several consecutive days.
Mechanism of action
Predominantly pharmacodynamic: acetaminophen metabolite (NAPQI) interferes with vitamin K cycle, reducing vitamin K–dependent clotting factor synthesis; minor/uncertain PK contribution.
Clinical management
Prefer the lowest effective paracetamol dose; limit to ≤2 g/day when possible. If using ≥2 g/day for >2–3 days, check INR within 3–5 days of initiation or dose increase and again after discontinuation; adjust warfarin as needed; counsel on bleeding.
Drug reference
References
- Warfarin (Coumadin) Prescribing Information – Drug Interactions — FDA Label
- Warfarin: Drug Interactions — Lexicomp
Frequently asked questions
Can I take paracetamol with warfarin?
The interaction is rated: Moderate. Paracetamol can increase INR and bleeding risk in warfarin-treated patients, especially with ≥2–3 g/day for several consecutive days.
How serious is the interaction between paracetamol and warfarin?
The interaction is rated: Moderate. Evidence level: Moderate.
How is the interaction between paracetamol and warfarin managed?
Prefer the lowest effective paracetamol dose; limit to ≤2 g/day when possible. If using ≥2 g/day for >2–3 days, check INR within 3–5 days of initiation or dose increase and again after discontinuation; adjust warfarin as needed; counsel on bleeding.
Why do paracetamol and warfarin interact?
Predominantly pharmacodynamic: acetaminophen metabolite (NAPQI) interferes with vitamin K cycle, reducing vitamin K–dependent clotting factor synthesis; minor/uncertain PK contribution.
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