HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY DETERMINATION OF DEXTROMETHORPHAN AND ITS METABOLITES IN URINE USING SOLID-PHASE EXTRACTION

A high performance liquid chromatography assay coupled with fluorescen ce detection was developed for the determination of dextromethorphan a nd its metabolites in urine. The products and the internal standard, p holcodine, were separated on an Alltima C18, 5 mu m column (250 x 4.6 mm): using a mobile phase containing sodium dodecyl sulphate (1 mM) in a mixture of acetonitrile-sodium dihydrogen phosphate (0.01 M) (40.5: 59.5, v/v) (pH = 2.5). A novel solid-phase extraction procedure with strong cation exchange, non end-capped, Isolute SCX cartridges allows good recovery of the products (mean 85% or more). For all analytes, th e assay is sensitive (LOQ 25 ng ml(-1), using 200 mu l urine), reprodu cible (RSD < 15%) and accurate (<15% deviation of the nominal value) o ver the range evaluated. This method can be used to measure dextrometh orphan and its metabolites to phenotype individuals as poor or extensi ve metabolizers of drugs metabolized by CYP2D6.