Development of a high pressure liquid chromatography method for the determination of mycophenolic acid and its glucuronide metabolite in small volumes of plasma from paediatric patients.

In order to facilitate the simultaneous determination of the levels of mycophenolic acid (MPA) and mycophenolic acid glucuronide (MPAG) in plasma samples a step wise gradient high performance liquid chromatography (HPLC) method was developed using UV detection system and naproxen as an internal standard. The analytes were extracted from plasma using Strata-X polymeric solid phase extraction (SPE) cartridges. Separation was achieved within a total chromatographic run time of 18 min at 1.0 ml/min flow rate using a Hv PURITY C18 column. The method was found to be linear over the concentration range investigated, 1.0-16 microg/ml (r > 0.99) for MPA and 10-160 microg/ml (r > 0.99) for MPAG. The limit of detection was 0.1 microg/ml for both MPAG and MPA. The intra- and inter-day imprecisions expressed as R.S.D. were 7.8 and 6.6%, respectively, for MPA (1 microg/ml) and 6.2% and 5.6%, respectively, for MPAG (20 microg/ml). The average extraction recovery from plasma was 93.06%, for MPA and 92.41% for MPAG. The method developed was found to be accurate and precise in quantifying the level of MPA and MPAG over a their therapeutic range of concentrations in small volumes of plasma and thus can be effectively used in the routine drug monitoring procedures and pharmacokinetic studies. It was also developed in such a way that it should be easily coupled to an electro-spray ionization mass spectrometer should greater sensitivity be required.