LC–MS/MS assay for olanzapine in human plasma and its application to a bioequivalence study

Abstract

This paper describes a selective and sensitive assay for the determination of olanzapine (OLZ) in human plasma based on liquid chromatography–tandem mass spectrometry (LC–MS/MS). The analyte and quetiapine as internal standard (IS) were extracted from 200 μL plasma via solid phase extraction on Waters Oasis HLB cartridges. Chromatographic separation was achieved on an ACE 5C18-300 column (100 mm×4.6 mm, 5 μm) under isocratic conditions in a run time of 3.5 min. Mass spectrometric detection involved electrospray ionization in the positive ion mode followed by multiple reaction monitoring (MRM) of the transitions at m/z 313/256 for OLZ and m/z 384/253 for the IS. The assay was linear in the range 0.10–40.0 ng/mL with a lower limit of quantitation and limit of detection of 0.10 and 0.012 ng/mL, respectively. Intra- and inter-day precision (as coefficient of variation) and relative recovery were <5.0% and >90%, respectively. The method was successfully applied to a bioequivalence study of 5 and 10 mg OLZ disintegrating tablets in 40 healthy Indian males with reproducibility by incurred sample reanalysis in the range −7.43 to 8.07%.