After receiving 4days of rivaroxaban 20mg twice daily to obtain supratherapeutic steady-state concentrations , volunteers were randomized to receive a single 50IUkg ( -1 ) bolus dose of four-factor PCC , three-factor PCC or saline 4h after the morning dose of rivaroxaban on day5 , and the effects of these interventions on prothrombin time and thrombin generation were determined .