ObjectiveTo establish a RP-HPLC method for determination of the concentrations of dextromethorphan and its metabolites dextrorphan in human urine.MethodsPhenacetine was used as internal standard,and the urine sample was hydrolyzed by enzyme,alkalified and extracted with hexane-butanol(91).The separation was carried out on DiamonsilTM C18 column (250 mm×4.6 mm,5 μm) with mobile phase of acetonitrile-1% triethylamine buffer solution (pH adjusted to 2.2 with H3PO4). Gradient elution was done for 0-15 min(20%-35% A). The flow rate was 1.0 ml/min. The detection wavelength was set at 280 nm and the column temperature was 40℃.ResultsThe linear ranges of dextromethorphan and dextrorphan were 0.05-2.0 μg/ml (r=0.999 9,n=5) and 0.5-20.0 μg/ml (r=0.999 9,n=5),respectively,and their lowest detecting concentrations were 0.04 μg/ml and 0.4 μg/ml,respectively.The intra-day and inter-day precision were both less than 10%.The low,middle and high extraction recoveries were between 94%-108%.ConclusionOur method is accurate and sensitive,and is suitable for the CYP2D6 phenotype analysis and pharmacokinetic studies of dextromethorphan and its metabolites in human.