Simultaneous Measurement of Mycophenolic Acid with Other Immunosuppressants in Whole Blood and Plasma by Using Liquid Chromatography–Tandem Mass Spectrometry

Therapeutic drug monitoring (TDM) of immunosuppressive drugs (ISDs) is essential for transplant recipients. The aim of this study is to establish an LC-MS/MS method to determine mycophenolic acid (MPA) and its metabolite, cyclosporin A (CsA), tacrolimus (TAC) and sirolimus (SRL) levels in whole blood and plasma simultaneously. Whole blood and plasma samples were treated with protein precipitation. After centrifugation, the supernatant was eluted through Agilent Eclipse XDB-C18 (3.5 μm, 2.1 mm × 100 mm) column by water (2 mmol/L ammonium formate) and methanol through a gradient method. The ISDs in renal allograft recipients were compared with TDM results. The methods established were linear within a range of 0.204-51 μg/mL for MPA, 2.0-500 μg/mL for MPAG, 4-1,000 ng/mL for CsA, 0.2-50 ng/mL for TAC and 0.2-50 ng/mL for SRL (r2 = 0.9998) in plasma and whole blood. The intra- and inter-day accuracy was in the range of 85-115%, and imprecision of all ISDs was <15%. Plasma MPA and MPAG levels can be estimated based on whole blood level: Cplasma = 1.52 × Cblood + 0.16 (r2 = 0.9168) and Cplasma = 1.58 × Cblood - 0.56 (r2 = 0.9069). The CsA (r2 = 0.9694, n = 60), TAC (r2 = 0.9426, n = 115) and SRL (r2 = 0.9484, n = 70) levels in whole blood were consistent with those obtained from the immunoassays. The LC-MS/MS method established is suitable for patients with various immunosuppressive regimens.