ドセタキセルとワルファリンの薬物相互作用によるプロトロンビン時間の変動に関する検討

Abstract

Warfarin is medicine whose dosage is determined by measuring the prothrombin time international normalized ratio (PTINR) as an index of anticoagulant activity because of its interactions with other medicines and the large inter-individual variability in its anticoagulant effect.We report a case in which unexpected PT-INR elevation was observed after chemotherapy that included docetaxel.The patient had been administered warfarin after aorta valve substitution due to valvular heart disease and then developed ovarian cancer.An interaction between warfarin and docetaxel was suspected because PT-INR was elevated within a few days of each chemotherapy session.In addition,we examined other patients who had been on both warfarin therapy and chemotherapy including docetaxel from August 2004 to December 2009.In these patients,the warfarin sensitivity index (WSI) was elevated significantly from its baseline value of 0.48.to 0.89 after chemotherapy.It is still uncertain whether there is a definite interaction between warfarin and docetaxel and no detailed mechanism for one has yet been reported.Nevertheless,it is necessary to assume the possibility of PT-INR elevation and to monitor PT-INR frequently in managing patients on both warfarin and chemotherapy.