title: Determination of S-1 (combined drug of tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and 5-fluorouracil in human plasma and urine using high-performance liquid chromatography and gas chromatography-negative ion chemical ionization mass spectrometry.
abstract: A high-performance liquid chromatography (HPLC) and gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICI-MS) method was developed for the analysis of the combined antitumor drug S-1 (tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and active metabolite 5-fluorouracil in human plasma and urine. Tegafur was fractionated from biological fluids by extraction with dichloromethane and analyzed by HPLC. 5-Fluorouracil and 5-chloro-2,4-dihydroxypyridine were extracted with ethyl acetate from the residual layer after extraction of tegafur, and converted to pentafluorobenzyl (PFB) derivatives. Potassium oxonate was cleaned up with an anion-exchange column (Bond Elut NH2). The extracted potassium oxonate was degraded to 5-azauracil and converted to PFB derivatives. The PFB derivatives were analyzed by GC-NICI-MS. A stable isotope was employed as the internal standard in the GC-NICI-MS analysis. The limits of quantitation of tegafur, 5-fluorouracil, 5-chloro-2,4-dihydroxypyridine and potassium oxonate in plasma were 10, 1, 2 and 1 ng/ml, respectively. The reproducibility of the analytical method according to the statistical coefficients is approximately 10%. The accuracy of the method is good; that is, the relative error is < 10%. The methods were applied to pharmacokinetic studies of S-1 in patients.
authors.affiliation: Pharmacokinetics Research Laboratory, Taiho Pharmaceutical Co. Ltd., Tokushima, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Matsushima
authors.forename: K
authors.initials: K
authors.lastname: Yoshida
authors.forename: R
authors.initials: R
authors.lastname: Kitamura
authors.forename: K
authors.initials: K
authors.lastname: Yoshida
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000032:analysis* / Q000097:blood / Q000652:urine; D002851:Chromatography, High Pressure Liquid; D004338:Drug Combinations; D004355:Drug Stability; D005472:Fluorouracil / Q000032:analysis* / Q000097:blood / Q000652:urine; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010094:Oxonic Acid / Q000032:analysis* / Q000097:blood / Q000652:urine; D011725:Pyridines / Q000032:analysis* / Q000097:blood / Q000652:urine; D012680:Sensitivity and Specificity; D005641:Tegafur / Q000032:analysis* / Q000097:blood / Q000652:urine
chemical_list: D004338:Drug Combinations; D011725:Pyridines; C079198:S 1 (combination); D005641:Tegafur; D010094:Oxonic Acid; D005472:Fluorouracil; C104201:gimeracil