HPLC determination of mycophenolic acid and mycophenolic acid glucuronide in human plasma with hybrid material

Abstract Mycophenolic acid (MPA), the active metabolite of the prodrug mycophenolate mofetil is an immunosuppressive agent which inhibits inosine monophosphate dehydrogenase. MPA is metabolised to phenolic glucuronide (MPAG) that may be hydrolysed in vivo to form free MPA. Drug monitoring is required in patients with multi-organ failure. Here, we report a HPLC method with organic/inorganic hybrid material for the simultaneous analysis of MPA and MPAG in human plasma. MPA and MPAG and carboxy butoxy ether mycophenolic acid (MPAC) used as internal standard were analysed on a bonded X-Terra column with a linear gradient elution mode using orthophosphoric acid and acetonitrile as eluents. Sample treatment procedure consists of deproteinisation with acetonitrile. Analytical recoveries were higher than 98 and 89% at concentrations ranging from 1 to 25 and 20 to 200 mg/L for MPA and MPAG, respectively. Calibration curves fitted by plotting the peak area ratio (compound of interest/internal standard) versus concentration were linear in the range 0.2–50 mg/L for MPA and in the range 1–500 mg/L for MPAG. The quantification limit was 0.2 mg/L for MPA and 1 mg/L for MPAG with a coefficient of variation less than 20% for a 500 μL sample volume. Intra- and inter-assay coefficient of variation was lower than 7% for all compounds. Detection was performed at 215 nm. Peak identity was confirmed through library matching by comparison with reference spectra. The X-Terra column provides good peak shape and may be used at low pH with a long life-time column. This HPLC method using a simple sample treatment procedure appears suitable for therapeutic drug monitoring in organ-transplant patients. The method is sensitive enough for monitoring MPA and MPAG during pharmacokinetic studies.