Characterization of the stereoselective metabolism of methadone and its primary metabolite via cyclodextrin capillary electrophoretic determination of their urinary enantiomers

Abstract

Using capillary zone electrophoresis with a phosphate buffer at pH 3, containing 4.3 mM hydroxypropyl-beta-cyclodextrin as chiral selector, the simultaneous separation of the enantiomers of methadone and its primary metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), is reported. After solid-phase extraction and analysis of the reconstituted extracts in a 60 cm fused-silica capillary of 50 microns ID within about 25 min, the mean S/R enantiomeric ratio of methadone in the urines of eight patients undergoing methadone therapy is shown to be 0.653 (range: 0.502-0.842). The mean enantiomeric ratio for the metabolite is 0.630 (range: 0.517-0.729). These data document the stereoselectivity of the methadone metabolism. Finally, the EDDP/ methadone ratio is shown to vary between 0.357 and 2.917 with a mean value of 1.731. The capillary electrophoretic assay described is simple, inexpensive and neither requires any sample derivatization, nor large amounts of organic solvents or expensive separation columns.

Sensitive chiral analysis by capillary electrophoresis

“…Briefly, offline SPE has been used for the extraction and preconcentration of drugs in biological samples and pesticides in water and food samples. Thus, the detection from 3610 28 to 5610 26 M of different drugs in plasma [64], serum [65], and urine [66,67] has been performed. In addition, the detection up to 10 210 or 10 27 M of phenoxy acid herbicides in spiked water samples [68,69] as well as the detection of the pesticides vinclozolin (,10 26 M), maleic hydrazide and imazalil (3610 27 M), in beverages and vegetables [70][71][72] has been achieved.…”

Toxicology and pathology of deaths related to methadone: retrospective review

“…• Necrotizing fasciitis occurring in methadone users seems to be more common than had previously been recognized; methadone may not be able to normalize the functioning of the immune system methadone isomers were understood, 8 before methadone metabolites could be routinely measured, before chiral (special chemical techniques used to separate dextro-from levo-isomers of the same molecule) separation of methadone isomers was possible 9 and before the problem of determining the redistribution of drugs after death was appreciated.…”

Recent advances in the applications of CE to forensic sciences (2001–2004)

“…The enantiomeric composition was used to infer the possible precursors used in their manufacture and the chemical process involved [30]. Following two papers by Lanz and Thormann [32] and Frost [33], a stereoselective method for the simultaneous determination of methadone and its two major metabolites 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline (EMDP) was developed by Kelly et al [34] by using 1 mM DM-b-CD in 100 mM phosphate buffer, pH 2.6.…”