Method for the quantitative analysis of cilostazol and its metabolites in human plasma using LC/MS/MS

An LC/MS/MS method for the simultaneous determination of cilostazol, a quin olinone derivative, and three active metabolites, OPC-13015. OPC-13213, and OPC-13217, in human plasma was developed and validated. Cilostazol, its me tabolites, and the internal standard, OPC-3930 were extracted from human pl asma by liquid-liquid partitioning followed by solid-phase extraction (SPE) on a Sep-Pak(TM) silica column. The eluent from the SPE column was then ev aporated and the residue reconstituted in a mixture of methanol/ammonium ac etate buffer (pH 6.5) (2:8 v/v). The analytes in the reconstituted solution were resolved using reversed-phase chromatography on a Supelcosil LC-18-DB HPLC column by an 17.5-min gradient elution. Cilostazol, its metabolites, and the internal standard were detected by tandem mass spectrometry with a Turbo Ionspray(TM) interface in the positive ion mode. The method was valid ated over a linear range of 5.0-1200.0 ng/ml for all the analytes. This met hod was demonstrated to be specific for the analytes of interest with no in terference from endogenous substances in human plasma or from several poten tial concomitant medications. For cilostazol and its metabolites, the accur acy (relative recovery) of this method was between 92.1 and 106.4%, and the precision (%CV) was between 4.6 and 6.5%. During the validation. standard curve correlation coefficients equalled or exceeded 0.999 for cilostazol an d its metabolites. These data demonstrate the reliability and precision of the method, The method was successfully cross-validated with an established HPLC method. (C) 2001 Elsevier Science B.V. All rights reserved.