Pharmacokinetic Profile of the Hepatitis C Virus NS5B Polymerase Inhibitor Sofosbuvir in Rats

An ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed to determine sofosbuvir in rat plasma using diazepam as the internal standard (IS). Sample preparation was accomplished through a protein precipitation procedure with acetonitrile to 0.1 mL plasma sample. The analyte and IS were separated on an Acquity UPLC BEH C18 column (2.1 mm x 50 mm, 1.7 mu m) with the mobile phase of acetonitrile and 0.1% formic acid in water with gradient elution at a flow rate of 0.40 mL/min. The injection volume was 2 mu L. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) by multiple reactions monitoring (MRM) of the transitions at m/z 530.3 -> 243.1 for sofosbuvir and m/z 285.2 -> 193.1 for IS. The linearity of this method was found to be within the concentration range of 10-2500 ng/mL with a lower limit of quantification of 10 ng/mL. Only 3.0 min was needed for an analytical run. The matrix effect was 94.0 to 98.5% for sofosbuvir. The intra-and inter-day precision (RSD%) were less than 8.3% and accuracy (RE%) was within +/- 8.2%. The recovery ranged from 75.1 to 83.3%. Sofosbuvir was sufficiently stable under all relevant analytical conditions. The method was also successfully applied to the pharmacokinetic study of sofosbuvir in rats. The pharmacokinetic parameters were demonstrated as followed: t(1/2) was 0.99 +/- 0.17 h, C-max was 1096.08 +/- 153.83 ng/mL, and AUC(0 ->infinity) was 2281.61 +/- 242.29 ng/mL. h.