Key result
Concomitant 5-fluorouracil linked to ~41% lower weekly warfarin dose.
Case Report (n=5)
No
Absolute Event Rate: 24% vs 40.66%
p-value: p=0.0026
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.
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Kolesar et al. (1999) conducted a case report in Patients receiving concomitant warfarin and 5-fluorouracil (n=5). Concomitant warfarin and 5-fluorouracil vs. Before starting chemotherapy was evaluated on Mean weekly warfarin dose (p=0.0026). Concomitant 5-fluorouracil administration reduced the mean weekly warfarin dose from 40.66 mg to 24 mg (p=0.0026), with all 5 patients requiring a dosage reduction and 2 hospitalized.
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