Comparison of VKA anticoagulation efficacy and the reversal anticoagulation effect of KO and vitamin K. (A) Comparison of the cell-based inhibition efficiency (IC₅₀) of the 4 VKAs on VKOR activity and the effective clinical dosages of these VKAs when used in the same patient for anticoagulation control. Clinical daily dosages of the VKAs were obtained from Johnson et al²⁶  and Undas et al.⁴³  (B-C) Cell-based functional study of reversing the anticoagulation effect of warfarin and fluindione by KO (B) or vitamin K (C). FIXgla-PC/HEK293 reporter cells were seeded in a multiwell cell culture plate with complete medium alone (Control) or complete medium containing 100 nM fluindione (F) or 100 nM warfarin (W). Twenty-four hours later, cell culture media were replaced with the same medium containing increasing concentrations of KO (B) or vitamin K (C). These cells were cultured another 24 hours for activity assay.