Methadone and methadone metabolites in postmortem specimens

We have determined drug/metabolite concentrations and ratios of methadone (METH) to two of its metabolites (EDDP, 2-ethylidene-1, 5-dimethyl-3, 3-diphenylpyrrolidine; and EMDP, 2-ethyl-5-methyl-3,3-diphenylpyrroline) in postmortem peripheral blood and liver tissue by liquid chromatography/tandem mass spectrometry. The assays employed deuterated internal standards and multiple reaction monitoring (MRM) techniques. The assay linear range was 0.01-2.0 mg/l for each analyte. METH, EDDP, and EMDP were determined in liver and peripheral blood from 46 methadone-positive cases. METH and EDDP were detected in all specimens, whether blood or liver. EMDP was detected, only in liver, and only 17 cases, at concentrations much lower than those of EDDP. Concentrations of METH and EDDP in blood and liver from EMDP-positive cases were in ranges higher than, but overlapping with, concentrations in blood and liver from EMDP-negative cases. These data suggest that although METH is readily demethylated and cyclized to EDDP, in vivo, conversion to EMDP may be less efficient and its accumulation in postmortem tissues may be highly individual.