Simultaneous determination of mycophenolic acid and its metabolites by HPLC and pharmacokinetic studies in rat plasma and bile.

In this study, we determined the pharmacokinetics of mycophenolic acid (MPA) and its metabolites mycophenolic acid glucuronide (MPAG) and acyl glucuronide (AcMPAG) in rat plasma and bile, using a newly developed HPLC method. Protein precipitation and liquid-liquid extraction were employed in sample preparation of plasma and bile, respectively. The HPLC methods included a gradient elution consisting of acetonitrile and phosphate buffer at a flow rate of 1.2 mL/min, with UV detection at 254 nm. The HPLC method was found to be sensitive and linear (r(2) ≥ 0.9991, 1.0-128.0 and 0.25-32.0 mg/L for MPA; 1.0-128.0 and 0.5-64.0 mg/L for MPAG; 0.25-32.0 and 1.0-128.0 mg/L for AcMPAG in rat plasma and bile, respectively), precise (both the intra- and inter-day variability were ≤ 6.8%), and accurate (both the intra- and inter-day accuracy were between 92.2% and 105.4%). The average extraction efficiencies for MPA, MPAG and AcMPAG were 85.3%, 100.1%, and 94.7% in plasma, and 88.0%, 67.3%, and 68.3% in bile, respectively. The method was successfully employed for pharmacokinetic studies in plasma and bile after oral administration of mycophenolate mofetil (prodrug of MPA) in rats.