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