Determination of the stereoselective aspects in in-vitro and in-vivo metabolism of the analgesic meptazinol by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method to separate meptazinol and its phase I metabolites has been developed using a LiChrosper 100 CN column and a mobile phase of trimethylammoniumacetate buffer (pH 5.5)-acetonitrile-methanol. Quantification of meptazinol and N-desmethylmeptazinol in biological samples was achieved by extraction with organic solvents and chromatographic analysis (detection limit 0.4 and 0.25 micrograms/ml, respectively). Afterwards the enantiomeric ratio of the two compounds was determined on a Chiral AGP column with a mobile phase of phosphate buffer (pH 7.0)-acetonitrile (alpha = 1.29 and 1.49, respectively). In-vitro metabolism data after incubation of the racemic compound and the enantiomers with liver supernatant and microsomes of different species are presented. Finally urinary data of two volunteers after oral application of the racemic drug were determined.