Stereospecific analysis of flurbiprofen and its major metabolites in plasma and urine by chiral-phase liquid chromatography

Direct chiral-phase HPLC methods have been developed for the determination of flurbiprofen and its major metabolites, namely 4'-hydroxyflurbiprofen and 3'-hydroxy-4'-methoxyfIurbiprofen, in biological fluids using a derivatized amylose chiral stationary phase (CSP; Chiralpak AD), Quantification of all three analytes, both free and conjugated, in urine was carried out following liquid-liquid extraction using tandem ultraviolet (UV) and fluorescence detection. Determination of flurbiprofen and the 4'-hydroxy- metabolite in plasma utilized the same CSP but required modification in the mobile phase composition and sole use of fluorescence detection. The urine assay was linear (r > 0.998) between 0.05-10 mug mL(-1), 0.1-20 muq mL(-1) and 0.01-2 mug mL(-1) for the enantiomers of flurbiprofen, 4'-hydroxyflurbiprofen and 3'-hydroxy-4'-methoxyflurbiprofen respectively. The plasma assay was linear (r > 0.997) between 0.1-6 mug mL(-1) and 0.01-0.6 mug mL(-1) for the enantiomers of flurbiprofen and 4'-hydroxyflurbiprofen respectively. Both assays, typically yielded within- and between-day imprecision and accuracy values less than 10% for the enantiomers of the different analytes. Initial volunteer studies suggest that the disposition of flurbiprofer displays modest enantioselectivity in humans