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 microL) was injected onto a Zorbax Eclipse XDB C(18) column (150 mm x 4.6 mm I.D., 5 microm 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 (r(2)>0.994) from 1.0-40 microg/mL with intra- and inter-day precision <15% and accuracy >95%. The method's improved sensitivity (LOQ=1.0 microg/mL) and minimal sample processing allowed rapid monitoring of MPA in human plasma.