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Warfarin—5‐FU Interaction — A Consecutive Case Series
Author(s) -
Kolesar Jill M.,
Johnson Carrie L.,
Freeberg Betty L.,
Berlin Jordan D.,
Schiller Joan H.
Publication year - 1999
Publication title -
pharmacotherapy: the journal of human pharmacology and drug therapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 109
eISSN - 1875-9114
pISSN - 0277-0008
DOI - 10.1592/phco.19.18.1445.30897
Subject(s) - warfarin , series (stratigraphy) , medicine , atrial fibrillation , biology , paleontology
Five patients from a single institution received concomitant warfarin and 5‐fluorouracil (5‐FU) during a 3‐year period. The mean weekly warfarin dose before starting chemotherapy was 40.66 mg and during chemotherapy it was 24 mg (p=0.0026). All patients required a warfarin dosage reduction (range 18–74%, mean 44%). Two patients were hospitalized, one with a major retroperitoneal bleed, the other for fresh‐frozen plasma administration and observation. Maximum international normalized ratios (INRs) ranged from 3.66–23.7. This series confirms a common, clinically significant interaction between warfarin and 5‐FU. An interaction between capecitabine, the orally available prodrug of 5‐FU, and warfarin also has been reported. We recommend weekly monitoring of prothrombin time and INR for all patients receiving concomitant warfarin and 5‐FU or capecitabine.