Stereoselective quantification of methadone and its major oxidative metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, in human urine using high-performance liquid chromatography

A stereoselective HPLC assay was developed for the quantification of the en antiomers of methadone and its major oxidative metabolite, 2-ethylidene-1,5 -dimethyl-3,3-diphenylpyrrolidine (EDDP) in human urine. The compounds were quantified in a single assay following liquid-liquid extraction and stereo selective HPLC with UV detection. Calibration curve concentrations ranged f rom 0.125 to 12.5 mu M for each enantiomer. Assay performance was assessed using quality control samples, and the inter- and intra-assay bias (<10%) a nd precision (<15%) were acceptable for all compounds. The assay was succes sfully used to quantitate the enantiomers of methadone and EDDP in urine sa mples obtained from subjects receiving methadone maintenance therapy. (C) 2 000 Elsevier Science B.V. All rights reserved.