title: Protein-binding high-performance frontal analysis of (R)- and (S)-warfarin on HSA with and without phenylbutazone.
abstract: Applicability of high-performance frontal analysis (HPFA) to the stereoselective study of drug-drug interaction upon plasma protein binding has been investigated. Racemic warfarin and phenylbutazone were used as model drugs. An on-line HPFA/HPLC system consisting of a HPFA column (diol-silica column), an extraction column, and a chiral separation column was developed, and human serum albumin solution containing racemic warfarin and/or phenylbutazone was injected directly to the HPFA column. When the injection volume was large enough, the binding equilibrium in the sample solution was reproduced in the column, and consequently a plateau region appeared on the chromatogram. This plateau region contains unbound drug(s). A given volume of eluent in the plateau part was transferred into the extraction column by column-switching. The concentrated drug(s) was then transferred to the chiral separation column to determine the unbound concentrations of the enantiomers and/or the competitor. The results agreed with those obtained by a conventional ultrafiltration-HPLC method. The influence of phenylbutazone upon the protein binding of warfarin is enantioselective. In warfarin and human serum albumin mixed solution, the unbound concentration of (R)-warfarin was 1.22 times higher than that of the S-isomer. By addition of phenylbutazone, the unbound concentration of (S)-warfarin increased more than that of (R)-warfarin, resulting in the reversed enantioselectivity, i.e., the unbound concentration of (S)-warfarin became 1.19 times larger than that of (R)-warfarin. The present method was also applicable to human plasma samples.
authors.affiliation: Faculty of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Japan.
authors.forename: J
authors.initials: J
authors.lastname: He
authors.forename: A
authors.initials: A
authors.lastname: Shibukawa
authors.forename: S
authors.initials: S
authors.lastname: Tokunaga
authors.forename: T
authors.initials: T
authors.lastname: Nakagawa
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D010653:Phenylbutazone / Q000097:blood / Q000378:metabolism*; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*; D013237:Stereoisomerism; D014859:Warfarin / Q000097:blood / Q000378:metabolism*
chemical_list: D012709:Serum Albumin; D014859:Warfarin; D010653:Phenylbutazone