ModerateAnilides. Analgesics and antipyretics×Vitamin K antagonist anticoagulants
Updated · Methodology
Mechanism
Paracetamol at doses above 3 g/day for more than 7 days raises INR by 1–1.5 via hepatocyte suppression and weak effect on warfarin metabolism. A single 0.5–1 g dose is safe.
Symptoms
Gum bleeding, epistaxis, bruising without trauma, black or tarry stools, haematuria. Higher risk in older patients, prior peptic ulcer disease, and chronic kidney disease.
Management
Paracetamol remains the analgesic and antipyretic of choice on warfarin, but for chronic use cap at 2 g/day. For full-dose courses longer than 4 days: check INR after a week; if above target, reduce warfarin by 10%.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- Pharmaceutical Press: Stockley's Drug Interactions, 12th edition (2024)– Preston CL (ed.). Stockley's Drug Interactions. 12th ed. London: Pharmaceutical Press; 2024
- AGS: American Geriatrics Society Beers Criteria for Potentially Inappropriate Medication Use (2023)– By the 2023 American Geriatrics Society Beers Criteria Update Expert Panel. AGS Beers Criteria for Potentially Inappropriate Medication Use in Older Adults. J Am Geriatr Soc 2023;71(7):2052-2081.
- FDA: Warfarin sodium tablet (Amneal Pharmaceuticals LLC) – Prescribing Information (2017)– ; DailyMed setid 558b7a0d-5490-4c1b-802e-3ab3f1efe760
- AEMPS: Ficha técnica: Paracetamol (nº registro 69478), sección 4.5 (2025)– AEMPS, CIMA, nº registro 69478, revisión 02/2025, sección 4.5