Simultaneous determination of cortisol, dexamethasone, methylprednisolone, prednisone, prednisolone, mycophenolic acid and mycophenolic acid glucuronide in human plasma utilizing liquid chromatography–tandem mass spectrometry

Chronic combination immunosuppressive regimens are commonly prescribed to renal transplant recipients. To develop an assay method for pharmacokinetic studies and therapeutic drug monitoring of multiple immunosuppressives, a liquid chromatography–tandem mass spectrometry (LC/MS/MS) approach for the simultaneous analysis of several glucocorticoids, mycophenolic acid (MPA) and mycophenolic acid glucuronide (MPAG) was investigated. The resultant method utilized a gradient reverse phase separation over a Symmetry C18 column using an ammonium acetate–methanol mobile phase at pH 3.5. The analytes were detected by coupling the chromatography system via electrospray to a triple quadrupole mass spectrometer. Multiple-reaction monitoring in the negative mode ion (MH-/product) was employed selecting MPA at 319.1/190.9, MPAG at 495.1/191.0, dexamethasone at 391.0/361.0, hydrocortisone at 361.1/331.1, methylprednisolone at 373.1/343.1, prednisone at 357.1/327.2, and prednisolone at 359.1/329.1. The calibration curve concentrations ranged from 3.60 ng/mL to 50 μg/mL with the lowest limit of quantitation for corticosteroids being 3.60–7.20 ng/mL and 0.656–6.75 μg/mL for MPA and MPAG, respectively. The relative standard deviation for quality control intraday variation and interday variation was between 0.76% and 9.57% for all analytes. This assay offers a versatile, unique method for multi-analyte immunosuppressive determinations during combination immunosuppression.