CriticalAntineoplastic, pyrimidine analogue (5-FU)×Vitamin K antagonist anticoagulants
Updated · Methodology
Mechanism
5-FU inhibits CYP2C9 (S-warfarin metabolism) and impairs vitamin K-dependent clotting factor synthesis through direct myelotoxicity. INR rises 2-4 fold within 5-10 days. Fatal bleeding cases reported.
Symptoms
Gum/nose bleeding, haematuria, bloody stool within 5-10 days. INR above 5.0.
Management
If possible – switch warfarin to LMWH during chemotherapy. If warfarin needed – reduce by 30-50% with weekly INR.
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
- AEMPS: Ficha tecnica de Fluorouracilo (5-FU) (2023)– AEMPS CIMA, 2023