Determining the Concentrations of Omeprazole and its Two Metabolites in Human Plasma by HPLC: Applications for Pharmacokinetic Studies

The goal of this study was to develop a simple high performance liquid chromatographic method to determine the concentrations of omeprazole and its metabolites, 5-hydroxyl omeprazole (5-OH OME) and omeprazole sulfone (OMEF) in human plasma and apply these data to pharmacokinetic studies. Omeprazole, its metabolites and the internal standard (phenacetin) were extracted from plasma samples with ethyl acetate and n-hexane, separated on a Zorbax SE-C18 column (4.6x150 nun, 5 mu m, Agilent, USA) with an acetonitrile-water-0.1% trifluoroacetic acid mobile phase at a flow rate of 1.0 mL/min. The UV detection wavelength was 302 nm (0-5.2 min); 262 nm (5.2-7.0 min) and 302 mu (7.0-16 min), these detection wavelengths refer to 380 nm. The calibration curve were linear from 0.010 similar to 2.0 mu g/mL for omeprazole and 0.005 similar to 1.0 mu g/mL for 5-OH OME and OMEF, with r = 0.999 7, r = 0.999 8, and r = 0.999 9, respectively. The method was specific and sensitive for determining the time course of plasma omeprazole concentration in 30 healthy volunteers after oral administration of 40 mg of omeprazole.Pharmacology & PharmacySCI(E)0ARTICLE5646-6503