Using HPLC-ESI-MS/MS, a validated protein precipitation was used to estimate the amount of rivaroxaban in human plasma, with rivaroxaban-D4 serving as an internal reference. Using an Infinity Poroshell 120 EC C18 (2.1×50mm, 1.9µm) column, 20mM ammonium acetate (pH 3.5) was combined with methanol and acetonitrile (20:20:60 v/v) to create the desired chromatographic conditions. The analysis lasted three minutes in total, with a 0.5 ml/min flow rate. The mass transitions of 440.1→144.9 and 436.1→144.9 for rivaroxaban and rivaroxaban-D4 were found, respectively. Using a quadratic regression model, the standard curve displays a correlation coefficient (r2) greater than 0.9998 and a linearity range of 1.00 to 14.00pm/ml.