Simple high-performance liquid chromatographic assay, with post-column derivatization, for simultaneous determination of mycophenolic acid and its glucuronide metabolite in human plasma and urine

Two simple high-performance liquid chromatographic (HPLC) methods have been established for simultaneous determination of mycophenolic acid (MPA) and its glucuronide metabolite (MPAG) in human urine, and of their total and unbound forms in human plasma. For total MPA and MPAG analysis sample preparation entailed precipitation of protein with acetonitrile and isolation of the free analytes from the plasma by ultrafiltration. For urine samples, fivefold dilution with water was used. MPAG was determined by UV detection whereas MPA was quantified by fluorescence detection after post-column derivatization with 0.2 M sodium hydroxide solution. For plasma, response was found to be linearly dependent on concentration over the ranges 0.1-40 mu g mL(-1) and 0.01-1 mu g mL(-1) for total and free MPA, respectively, and 10-200 mu g mL(-1) and 2.5-100 mu g mL(-1) for total and free MPAG, respectively. For urine, linearity was observed from 0.1 to 50 mu g mL(-1) for MPA and 10 to 500 mu g mL(-1) MPAG in the urine before dilution. The methods reported were found to be accurate and reproducible for quantifying the level of MPA and MPAG and can thus be used for clinical pharmacokinetic studies and for therapeutic drug monitoring.