title: Enantioselective quantification of omeprazole and its main metabolites in human serum by chiral HPLC-atmospheric pressure photoionization tandem mass spectrometry.
abstract: Omeprazole is a proton pump inhibitor drug in widespread use for the reduction of gastric acid production. It is also proposed as a test substance for the phenotyping of cytochrome CYP3A4 and CYP2C19 enzyme activities. For this purpose, it is necessary to quantify, additionally to omeprazole, the two main metabolites 5-hydroxyomeprazole and omeprazole-sulfon in human plasma. Since omeprazole is a racemic mixture of two enantiomers and its enzymatic decomposition depends in part on its chiral configuration, full information about its metabolic breakdown can only be gained by enantioselective quantification of the drug and its metabolites. We introduce a new LC-MS/MS method that is capable to simultaneously quantify omeprazole and its two main metabolites enantioselectively in human serum. The method features solid-phase extraction, normal phase chiral HPLC separation and atmospheric pressure photoionization tandem mass spectrometry. As internal standards serve stable isotope labeled omeprazole and 5-hydroxyomeprazole. The calibration functions are linear in the range of 5-750 ng/ml for the omeprazole enantiomers and omeprazole-sulfon, and 2.5-375 ng/ml for the 5-hydroxyomeprazole enantiomers, respectively. Intra- and inter-day relative standard deviations are <7% for omeprazole and 5-hydroxyomeprazole enantiomers, and <9% for omeprazole-sulfon, respectively.
authors: Institute of Clinical Pharmacology, Otto-von-Guericke University, Leipziger Strasse 44, 39120 Magdeburg, Germany. jens.martens-lobenhoffer@med.ovgu.de
authors: Jens
authors: J
authors: Martens-Lobenhoffer
authors: Ines
authors: I
authors: Reiche
authors: Uwe
authors: U
authors: Tröger
authors: Klaus
authors: K
authors: Mönkemüller
authors: Peter
authors: P
authors: Malfertheiner
authors: Stefanie M
authors: SM
authors: Bode-Böger
mesh_terms: D000897:Anti-Ulcer Agents / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D001274:Atmospheric Pressure; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008027:Light; D009853:Omeprazole / Q000031:analogs & derivatives* / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D011786:Quality Control; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013997:Time Factors
chemical_list: D000897:Anti-Ulcer Agents; D009853:Omeprazole