Effect of oral administration of warfarin on blood coagulation in the common carp

The anticoagulant effect of potassium warfarin and the antagonistic effect of vitamin K3 a-gainst warfarin were examined using common carp. Three different dosages of warfarin with and without supplementary vitamin K3 were orally administered to common carp for 10-14 days, and prothrombin time (PT) and activated partial thromboplastin time (APTT) were measured at in-tervals of 3-7 days. At dosages of 2.0 and 1.0mg/kg/day of warfarin, prolongation of PT and APTT was observed. Supplementation of vitamin K3 was effective in preventing the prolongation of PT at a dosage of 1.0mg of warfarin, but it was not effective at 2.0mg. On the other hand, supplementation of vitamin K3 could not prevent prolongation of APTT with any warfarin dosage used, indicating that the antagonistic effect of vitamin K3 against warfarin is limited to PT.