Simultaneous quantification of mycophenolic acid and its glucuronide metabolites in human plasma by an UPLC–MS/MS assay

The aim of this study was to develop a reliable UPLC–MS/MS assay for accurate quantification of mycophenolic acid (MPA) and its glucuronide conjugates in human plasma. Plasma proteins were precipitated with acetonitrile and the chromatographic separation was achieved on a C₁₈ column with a gradient elution. The detection was performed by a triple quadrupole mass spectrometer in the positive electrospray ionization and multiple reaction monitoring mode. Linearity of the assay was demonstrated over the range of 20–10,000 ng/mL for MPA and MPA glucuronide (MPAG), and 2–1000 ng/mL for acyl MPA glucuronide in human plasma. The assay was precise and accurate with coefficient of variation and bias <15%. MPA and MPAG were stable at 25 °C up to 1 day in both heparin‐ and EDTA‐treated blood. In heparin‐ and EDTA‐plasma, MPA and MPAG were stable for at least 1 week at 25 and 4 °C, and 1 month at ?20 °C. However, 99% acyl MPA glucuronide degraded in both heparin‐ and EDTA‐blood as well as plasma when stored at room temperature for 1 day. All the analytes remained stable for at least 3 months in acidified EDTA‐plasma at ?80 °C. The assay was successfully applied on patients post hematopoietic stem cell transplantation. Copyright © 2016 John Wiley & Sons, Ltd.