title: Stereospecific gas chromatographic method for determination of methadone in serum.
abstract: rac-Methadone is used clinically for the chronic maintenance treatment of heroin addiction and for the relief of pain. As the pharmacological activity of methadone is due primarily to the (-)-(R)-enantiomer, stereospecific measurements of methadone serum concentrations in methadone-treated patients are expected to be more relevant for clinical studies than earlier described total drug measurements. This study describes a stereospecific gas chromatographic (GC) method for the determination of methadone in serum. The extracted methadone was derivatizised with (-)-menthyl chloroformate. The diastereometric derivatives were analysed by GC on a capillary column and detected with a nitrogen-phosphorus detector. The resolution factor obtained for the methadone enantiomers was 1.1 with a relatively short time of analysis (30 min). By analysing the pure (-)-(R)-enantiomer, no racemization was seen during the analysis. The lower limit of quantitation was 75 nmol/l for each enantiomer. Measurements of the ratio between (-)-(R)- and (+)-(S)-methadone concentrations in serum from five methadone-treated patients showed interindividual differences (range 0.5-1.1). The patient results correlated well with those from another GC method measuring total methadone.
authors.affiliation: Royal Danish School of Pharmacy, Copenhagen.
authors.forename: K
authors.initials: K
authors.lastname: Kristensen
authors.forename: H R
authors.initials: HR
authors.lastname: Angelo
mesh_terms: D002849:Chromatography, Gas; D006801:Humans; D007202:Indicators and Reagents; D008691:Methadone / Q000097:blood*; D013237:Stereoisomerism
chemical_list: D007202:Indicators and Reagents; D008691:Methadone