Simple high performance liquid chromatographic assay for mycophenolic acid in renal transplant patients

A selective and highly accurate HPLC-UV method is described to determine plasma concentrations of mycophenolic acid (MPA), the active metabolite of the prodrugs Cellcept® and Myfortic®. The method is simple and utilizes acidification of plasma and protein precipitation step using a mixture of acetonitrile and phosphate buffer (pH 3). Following vortex mixing and centrifugation, the supernatant (50 μL) was injected onto a Zorbax Eclipse XDB C18 column (150 mm × 4.6 mm I.D., 5 μm particle size). A mobile phase composed of acetonitrile and 0.1 M phosphate buffer, pH 3 (43:57) delivered at 1.0 mL/min produced peaks for MPA and the internal standard (Naproxen) in <7 min. Calibration curves were linear (r2 > 0.994) from 1.0–40 μg/mL with intra- and inter-day precision <15% and accuracy >95%. The method's improved sensitivity (LOQ = 1.0 μg/mL) and minimal sample processing allowed rapid monitoring of MPA in human plasma.