Chirial Inversion And Tissue Distribution Of Rivaroxaban In Rats

Rivaroxaban is a selectively direct inhibitor of clotting factor(Factor Xa). Because of its anticoagulant effect, it is widely used for the prophylaxis and treatment of venous thromboembolism. There are many researches about pharmacokinetics of rivaroxaban, but few reports about the stereoselective pharmacokinetics of rivaroxaban enantiomers. Therefore, it is necessary to further study it to ensure not only the efficacy but also the safety of rivaroxaban for avoiding the tragedy of the thalidomide event. This article is aim at investigating the chiral inversion part of stereoselective pharmacokinetics of rivaroxaban enantiomers in rat. Meanwhile, we also developed and validated an efficient and rapid UPLC-MS/MS method to separate and analysis rivaroxaban enantiomers. At end of this research, the rat tissue distribution of rivaroxaban was also investigated by an oral administration after 24 h. The results of the experiments are as follow:Rivaroxaban enantiomers were successfully separated by Chiralpak IC column, and the optimized conditions of chromatogram and mass sprctrum were obtained: H2O-acetonitrile=10:90 was used as mobile phase at 0.4 mL/min flow rate, the column temperature maintained at 25 ?. The detection was performed by positive electrospray ionization(ESI) with multiple reaction monitoring(MRM) transitions of m/z 436.00>144.87 for rivaroxaban enantiomers. The capillary voltage, cone voltage and collision energy were 3.5 kV, 44 V and 28 V respectively. The limit of detection(LOD) and limit of quantification(LOQ) were 0.39 and 1.3 ng/mL, the accuracy was between 94.8% and 100.5%, the precision RSD was below 2%, and there was a excellent linearity and correlation coefficient(r2=0.9959) between the peak area and the concentration of S-rivaroxaban which ranged from 2 ng/mL to 200 ng/mL. These results indicated that this method is effective, sensitive and accurate for separating and analyzing rivaroxaban enantiomers.Respectively drawing rat blood within absorption phase, balance phase and elimination phase after a single oral administration with 4.0 mg/kg R-rivaroxaban, and analyzing rivaroxaban enantiomers in blood were able to get those results as follows: R-rivaroxaban was rapidly and mostly unidirectional biotransformed to S-rivaroxaban within 30 min, and the plasma concentration of S-enantiomer reached the maximum value(Cmax=1842 ng/mL) at 2 h(tmax) after administration, however, in the whole process, the plasma concentration of R-rivaroxaban almost closed to zero. In S-rivaroxaban group, S-enantiomer could not biotransformate to R-enantiomer, and the Cmax of Srivaroxaban(327.2 ng/mL) reached at tmax =1 h.After a single oral administration 4.0 mg/kg rivaroxaban 24 h to rats, the order of rivaroxaban content in different tissues was: lung(279.7 ng/mL)> liver(228.044 ng/mL)> kidney(179.284 ng/mL).