Simultaneous Determination of Dextromethorphan and Three Metabolites in Plasma and Urine Using High-Performance Liquid Chromatography with Application to Their Disposition in Man

Abstract

A simple, sensitive, and reproducible high-performance liquid chromatography assay is described for the simulataneous determination of dextromethorphan, dextrorphan, 3-hydroxymorphinan, and 3-methoxymorphinan in plasma and urine. A conventional solvent-solvent extraction procedure was used for the isolation of the analytes from plasma and urine samples. The compounds were separated on a cyano column (150 .times. 4.6 mm, 5-.mu.m particle size) using a mobile phase of acetonitrile/triethylamine/distilled water (17:0.06:82.94, vol/vol), pH 3.0, and then were measured by fluorescence detection. Calibration curves in the range 2-200 ng/ml for plasma and 0.05-10 .mu.g/ml for urine were linear and passed through the origin. The precision and accuracy were >90% and the lowest detectable concentrations were 0.5 ng/ml for 3-hydroxymorphinan and 3-methyoxymorphinan and 1 ng/ml for dextramethorphan and dextrophan in plasma. The utility of this method is demonstrated in a preliminary study of dextromethorphan metabolism and pharmacokinetics in man.