@article{oai:u-ryukyu.repo.nii.ac.jp:02019613, author = {Tayag, Jose Carlos S. and Ishii, Takeo and Kokuba, Shun and Hirata, Tetsuo and Shiohira, Hideo and Nakamura, Katsunori}, issue = {8}, journal = {Biological and Pharmaceutical Bulletin}, month = {}, note = {Drug–drug interactions (DDIs) between warfarin (WF) and fluoropyrimidines are well known. Co-administration of WF and 5-fluorouracil (5-FU) leads to elevations in prothrombin time international normalised ratio (PT-INR). The inhibition of drug metabolism through suppression of CYP activity is a possible cause of prolonged PT-INR elevations. 5-FU and its metabolites are suspected to inhibit CYPs, but the precise mechanisms of action remain unknown. This study aimed to investigate the possible DDI effects of the co-administration of 5-FU with WF using PT-INR and PT-INR/dose ratio as pharmacodynamic parameters. Retrospective case series data were collected from patients who received parenteral 5-FU chemotherapy from April 2009 to December 2019 at the University of the Ryukyus Hospital. Seven patients who received 5-FU in combination with WF were analysed. There was a significant increase in PT-INR and PT-INR/dose during the co-administration of WF and 5-FU (p= 0.0018 and p= 0.0187, respectively; paired t-test). The findings demonstrated significant DDI between 5-FU and WF evident as elevated PT-INR and PT-INR/dose ratio.}, pages = {1101--1105}, title = {Changes in Pharmacodynamic Parameters during Co-administration of 5-FU with Warfarin: A Retrospective Case Series}, volume = {45}, year = {2022} }