Abstract
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.
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