Fluoropyrimidines, including 5-fluororacil (5-FU), cause gastrointestinal damage in the clinical setting and might affect the gastrointestinal absorption of concomitantly administered drugs. We aimed to evaluate the effects of fluoropyrimidine-induced gastrointestinal damage on the pharmacokinetics and pharmacodynamics of dabigatran etexilate (DABE), an anticoagulant, in rats with gastrointestinal damage induced by the repeated oral administration of 5-FU. Rats were administered DABE orally or dabigatran (DAB), an active moiety of DABE, intravenously. The plasma DAB concentration was determined using liquid chromatography-tandem mass spectrometry. The activated partial thromboplastin time (APTT) was measured before and 30 min after the administration of each drug, and the APTT ratio was calculated. In 5-FU-treated rats, the maximum plasma concentration, the area under the concentration-time curve of DAB after the oral administration of DABE, and the oral bioavailability of DABE were significantly decreased to 18.3%, 22.9%, and 16.3% of the respective control values. The 5-FU-treated rats’ APTT ratio was also significantly lower than the control value. Fluoropyrimidine-induced gastrointestinal damage might reduce the plasma concentration of DAB by impairing DABE absorption and might attenuate the anticoagulant effects of DABE in the clinical setting.
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