MEASUREMENT OF DEXFENFLURAMINE METABOLISM IN RAT-LIVER MICROSOMES BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A specific and useful method was developed for the determination of de xfenfluramine metabolism by microsomal systems utilising GC-MS, The sy nthesis of two metabolites 1-(3-trifluoromethylphenyl)propan-2-ol ('al cohol') and 1-(3-trifluoromethylphenyl)-l,2-propanediol ('diol') via s traightforward routes, were confirmed by MS and NMR spectra, The condi tions for extraction from alkalinised microsomal mixtures of the metab olites nordexfenfluramine, 1-(3-trifluoromethylphenyl)propan-2-one ('k etone'), alcohol and diol, their conversion to trifluoroacetate deriva tives and analysis by GC-MS-SIM are described. Calibration curves were constructed between 48 and 9662 nM and fitted to quadratic equations (r(2)>0.999), The method precision was good over low (121 nM) medium ( 2415 nM) and above medium (9662 nM) concentrations for all metabolites ; the within- and day-to-day coefficients of variation ranged between 2.5-12.4% and 6.7-17.5%, respectively. The accuracy, measured as bias, was very good both within- and day-to-day (range: -0.4-12.6%, 0.8-18. 9%). For most metabolites, the C.V, for the assay and bias increased a t 121 nM. Dexfenfluramine metabolism by rat liver microsomes was inves tigated using the assay method and showed a concentration dependent in crease in nordexfenfluramine and ketone metabolites over the substrate range of 5-200 mu M.