ENANTIOSELECTIVE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY DETERMINATIONOF METHADONE ENANTIOMERS AND ITS MAJOR METABOLITE IN HUMAN BIOLOGICAL-FLUIDS USING A NEW DERIVATIZED CYCLODEXTRIN-BONDED PHASE

The simultaneous determination of methadone (Mtd) enantiomers and its major metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (E DDP), in human urine and serum by enantioselective HPLC using a new Cy clobond I-2000 RSP column is described. After alkaline extraction from urine or serum with estazolam as an internal standard, Mtd enantiomer s and its metabolite (EDDP) are separated on the previous column with reversed-mobile phase and detected at 210 nm, Peak resolutions are abo ut 2.0 for Mtd enantiomers. The relative standard deviations (R.S.D.) of Mtd and EDDP standards are between 0.5 and 4.5%. Most drugs of abus e are shown not to interfere with this technique. The method has been applied to study the levels of each Mtd enantiomer and of its racemic metabolite in urine and serum of patients under maintenance treatment for opiate dependence. In urine, R-(-)-Mtd levels are always higher (a bout 2+/-0.5-fold) than those of S-(+)-Mtd and in most cases, metaboli te concentrations are greater than those of global Mtd enantiomers. Ho wever, the R-(-) enantiomer levels of residual drug in serum of some p atients were lower than those of its antipode. This method is suitable for pharmacokinetic and toxicological studies of Mtd enantiomers and its major metabolite in biological fluids. (C) 1997 Elsevier Science B .V.