title: Warfarin-5-FU interaction--a consecutive case series.
abstract: 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.
authors.affiliation: School of Pharmacy, University of Wisconsin-Madison, 53706-1515, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Kolesar
authors.forename: C L
authors.initials: CL
authors.lastname: Johnson
authors.forename: B L
authors.initials: BL
authors.lastname: Freeberg
authors.forename: J D
authors.initials: JD
authors.lastname: Berlin
authors.forename: J H
authors.initials: JH
authors.lastname: Schiller
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D000069287:Capecitabine; D003841:Deoxycytidine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D004347:Drug Interactions; D005472:Fluorouracil / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D011517:Prothrombin Time; D012187:Retroperitoneal Space / Q000473:pathology; D013997:Time Factors; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D000970:Antineoplastic Agents; D003841:Deoxycytidine; D014859:Warfarin; D000069287:Capecitabine; D005472:Fluorouracil