title: Sensitive quantification of omeprazole and its metabolites in human plasma by liquid chromatography-mass spectrometry.
abstract: A sensitive method was developed for the simultaneous determination of omeprazole and its major metabolites 5-hydroxyomeprazole and omeprazole sulfone in human plasma by HPLC-electrospray mass spectrometry. Following liquid-liquid extraction HPLC separation was achieved on a ProntoSil AQ, C18 column using a gradient with 10 mM ammonium acetate in water (pH 7.25) and acetonitrile. The mass spectrometer was operated in the selected ion monitoring mode using the respective MH(+) ions, m/z 346 for omeprazole, m/z 362 for 5-hydroxy-omeprazole and omeprazol-sulfone and m/z 300 for the internal standard (2-{[(3,5-dimethylpyridine-2-yl)methyl]thio}-1H-benzimidazole-5-yl)methanol. The limit of quantification (LOQ) achieved with this method was 5 ng/ml for 5-hydroxyomeprazole and 10 ng/ml for omeprazole and omeprazole-sulfone using 0.25 ml of plasma. Intra- and inter-assay variability was below 11% over the whole concentration range from 5 to 250 ng/ml for 5-hydroxyomeprazol and from 10 to 750 ng/ml for omeprazole and omeprazole-sulfone. The method was successfully applied to the determination of pharmacokinetic parameters of esomeprazole and the two major metabolites after a single dose and under steady state conditions.
authors.affiliation: Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112, D-70376 Stuttgart, Germany. ute.hofmann@ikp-stuttgart.de
authors.forename: Ute
authors.initials: U
authors.lastname: Hofmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwab
authors.forename: Gerd
authors.initials: G
authors.lastname: Treiber
authors.forename: Ulrich
authors.initials: U
authors.lastname: Klotz
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D064098:Esomeprazole; D005764:Gastroesophageal Reflux / Q000097:blood; D006801:Humans; D009853:Omeprazole / Q000097:blood* / Q000378:metabolism / Q000493:pharmacokinetics; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D009853:Omeprazole; D064098:Esomeprazole