Determination of drug plasma concentrations
Trough plasma samples were obtained at 24 hours or 12 hours after last administered dose of rivaroxaban or apixaban respectively. Peak plasma samples were obtained on the same day of trough plasma samples, at 3 hours after intake of medication with food.
Plasma concentrations for rivaroxaban and apixaban were measured using high performance liquid chromatography-mass spectrometry (HPLC-MS). The lower limits of quantification (LLOQ) and upper limits of quantification (ULOQ) were 5 ng/mL and 1000 ng/mL for rivaroxaban, and 1 ng/mL and 500 ng/mL for apixaban.
Measured plasma concentrations below the LLOQs of the analytical methods were set to half of the LLOQ (LLOQ/2) of the respective analytical methods