High-performance size-exclusion chromatographic analysis of dextran–methylprednisolone hemisuccinate in rat plasma

A size exclusion chromatographic method is presented for the measurement of the concentrations of a macromolecular prodrug of methylprednisolone (MP), dextran–methylprednisolone succinate (DEX–MPS), in rat plasma. After precipitation of the plasma (100 μl) proteins with perchloric acid, the samples are injected into a size exclusion column with a mobile phase of water:acetonitrile:glacial acetic acid (75:25:0.2) and a flow-rate of 1 ml/min. The DEX–MPS conjugate, detected at 250 nm, elutes at a retention time of ∼6.5 min, free of endogenous peaks. Excellent linear relationships (r2=0.997) were found between the detector response and the concentrations of DEX–MPS in the range of 2–100 μg/ml (MP equivalent), with intra- and inter-run C.V.s of <6% and error values of <5%. The application of the assay was also demonstrated by measurement of the plasma concentrations of DEX–MPS after single 5 or 10 mg/kg doses of the conjugate administered intravenously to rats.