Quantitative analysis of methadone in biological fluids using deuterium-labeled methadone and GLC-chemical-ionization mass spectrometry.
The (+)-,(-)-, and (+/-)-2H5-methadones, which contained five deuterium atoms in one aromatic ring, were synthesized for use in clinical pharmacological studies and as internal standards. GLC-chemical-ionization mass spectrometry was used to determine plasma and urinary methadone levels by an inverse isotope dilution assay. Plasma drug levels could be determined to 10 pmoles/ml, and urine levels could be measured to 5 pmoles/ml. Plasma  methadone levels were examined in several patients undergoing methadone maintenance therapy. These levels generally ranged between 100 and 400 ng/ml (320-1300 pmoles/ml) after an average oral dose of 1 mg/kg/day. The methadone half-life was 28.8 +/- 4.8 hr.
D000328:Adult; D002849:Chromatography, Gas; D003903:Deuterium; D006801:Humans; D007553:Isotope Labeling; D013058:Mass Spectrometry; D008691:Methadone / Q000032:analysis* / Q000138:chemical synthesis; D008722:Methods; D013237:Stereoisomerism
D003903:Deuterium; D008691:Methadone