Rapid and simultaneous determination of mycophenolic acid and its glucuronide conjugate in human plasma by ion-pair reversed-phase high-performance liquid chromatography using isocratic elution

A high-performance liquid chromatographic method has been developed for the simultaneous determination of mycophenolic acid (MPA) and its glucuronide conjugate (MPAG) in human plasma. The method involves protein precipitation with acetonitrile, followed by ion-pair reversed-phase chromatography on C -18 column, with a 40 mM tetrabutyl ammonium bromide (TBA)-acetonitrile (65 :35, v/v) mobile phase. A 2D-mul volume of clear supernatant was injected a fter centrifugation, and the eluent was monitored at 304 nm. No interferenc e was found either with endogenous substances or with many concurrently use d drugs, indicating a good selectivity for the procedure. Calibration curve s were linear over a concentration range of 0.5-20.0 mug/ml for MPA and 5-2 00 mug/ml for MPAG. The accuracy of the method is good, that is, the relati ve error is below 5%. The intra- and inter-day reproducibility of the analy tical method is adequate with relative statistical deviations of 6% or belo w. The limits of quantification for MPA and MPAG were lower than 0.5 and 5. 0 mug/ml, respectively, using 50 mul of plasma. The method was used to dete rmine the pharmacokinetic parameters of MPA and MPAG following oral adminis tration in a patient with renal transplantation. (C) 2001 Elsevier Science B.V. All rights reserved.