High-performance liquid chromatographic determination of sulfinpyrazone and its metabolites in plasma

A specific sensitive reversed-phase high-performance liquid chromatographic method for simultaneous determination of sulfinpyrazone (Anturane) and five of its metabolites (p-hydroxy-sulfinpyrazone, p-hydroxy-sulfone, sulfone, p-hydroxy-sulfide, and sulfide) in plasma is described. The compounds were extracted from plasma, back-extracted, re-extracted and separated on a 10-micron muBondapak C18 column using 10 mmol/l orthophosphoric acid-acetonitrile-ethanol as the mobile phase. Phenylbutazone was used as internal standard, which was totally separated from all other compounds. The lower limit of sensitivity for sulfinpyrazone, sulfone, p-hydroxy-sulfide and sulfide is 30 ng/ml, and 100 ng/ml for p-hydroxy-sulfinpyrazone and p-hydroxy-sulfone. Concentrations of sulfinpyrazone between 0.5 and 25 micrograms/ml were measured with an average coefficient of variation of 5.1%. Examples of application of this assay are given.