Determination of rabeprazole and its active metabolite, rabeprazole thioether in human plasma by column-switching high-performance liquid chromatography and its application to pharmacokinetic study.
ABSTRACT A new sensitive column-switching high-performance liquid chromatographic (HPLC) method with ultraviolet detection was developed for the simultaneous determination of rabeprazole, a proton pump inhibitor, and its active metabolite, rabeprazole thioether in human plasma. Rabeprazole, its thioether metabolite and 5-methyl-2-[(4-(3-methoxypropoxy)-3-methyl pyridin-2-yl) methyl sulfinyl]-1H-benzimidazole, as an internal standard were extracted from 1 ml of plasma using diethyl ether-dichloromethane (9:1, v/v) mixture and the extract was injected into a column I (TSK-PW precolumn, 10 microm, 35 mmx4.6mm I.D.) for clean-up and column II (C18 Grand ODS-80TM TS analytical column, 5 microm, 250 mmx4.6 mm I.D.) for separation. The peak was detected with an ultraviolet detector set at a wavelength of 288 nm, and the total time for chromatographic separation was approximately 25 min. Mean absolute recoveries were 78.0 and 88.3% for rabeprazole and rabeprazole thioether, respectively. Intra- and inter-day coefficient variations were less than 6.5 and 4.5% for rabeprazole, 3.6 and 5.3% for rabeprazole thioether, respectively, at the different concentration ranges. The validated concentration ranges of this method were 1-1000 ng/ml for rabeprazole and 3-500 ng/ml for rabeprazole thioether. The limits of quantification were 1 ng/ml for rabeprazole and 3 ng/ml for rabeprazole thioether. The method was suitable for therapeutic drug monitoring and was applied to pharmacokinetic study in human volunteers.
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ABSTRACT: A reversed-phase high-performance liquid chromatographic method was developed and validated for the determination of rabeprazole in pharmaceutical dosage forms. The determination was performed on a Nucleodur column C8 (250×4.6 mm i.d., 5m particle size); the mobile phase consisted of a mixture of 0.1M formic acid and methanol (58:42, v/v), pumped at a flow rate 1.0 mL min−1. The photodiode array detector was operated at 280 nm. The retention times for rabeprazole and pantoprazole, which was used as internal standard, were 5.13 and 11.12 min, respectively. Linearity range (r2 better than 0.999, n=5) was 40-1600 g mL-1 with limit of detection value of 2.56g mL-1. The precision of the method was demonstrated using intra- and inter-day assay RSD values which were less than 2.82%, while the recovery was 100.07-104.54% (n=14). The method was applied in the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control.
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ABSTRACT: Rabeprazole is known to be a substrate of CYP2C19. Our objective was to evaluate the possible effect of an inhibitor of CYP2C19, fluvoxamine, and compare the inhibitory effect of fluvoxamine on the metabolism of rabeprazole between CYP2C19 genotypes. A two-way randomized double-blind, placebo-controlled crossover study was performed. Twenty-one volunteers, of whom seven were homozygous extensive metabolizers (EMs), eight were heterozygous EMs and six were poor metabolizers (PMs) for CYP2C19, received two 6-day courses of either fluvoxamine 50 mg or placebo daily in a randomized fashion with a single oral dose of rabeprazole 20 mg on day 6 in all cases. Plasma concentrations of rabeprazole and its metabolite rabeprazole thioether were monitored up to 24 h after dosing. During placebo administration, the mean AUCs(0,infinity) of rabeprazole in homozygous EMs, heterozygous EMs and PMs were 882 (95% CI, 602, 1162) ng ml-1h , 1214 (975, 1453) ng ml-1 h and 2762 (2482, 3042) ng ml-1 h (P<0.001), respectively. Fluvoxamine treatment increased AUC(0,infinity) of rabeprazole and rabeprazole thioether by 2.8-fold (P<0.001) and 5.1-fold (P<0.01) in homozygous EMs, and by 1.7-fold (P<0.01) and 2.6-fold (P<0.01) in heterozygous EMs, and significantly prolonged the elimination half-life of rabeprazole and rabeprazole thioether in homozygous EMs and in heterozygous EMs, whereas no difference in any pharmacokinetic parameters was found in PMs. There was a significant difference in fluvoxamine-mediated percentage increase in AUC(0,infinity) of rabeprazole and rabeprazole thioether between CYP2C19 genotypes. The present study indicates that there are significant drug interactions between rabeprazole and fluvoxamine in EMs of CYP2C19. It is predominantly involved in rabeprazole and rabeprazole thioether metabolism in EMs. Therefore, CYP2C19 is the key determinant of rabeprazole disposition in EMs.British Journal of Clinical Pharmacology 03/2006; 61(3):309-14. DOI:10.1111/j.1365-2125.2005.02556.x · 3.69 Impact Factor
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ABSTRACT: A simple and sensitive column-switching high-performance liquid chromatographic method was developed for the simultaneous determination of omeprazole and its two main metabolites, 5-hydroxyomeprazole and omeprazole sulfone, in human plasma. Omeprazole, its two metabolites and lansoprazol as an internal standard were extracted from 1 ml of alkalinized plasma sample using diethyl ether-dichloromethane (45:55, v/v). The extract was injected into a column I (TSK-PW precolumn, 10 microm, 35 mm x 4.6 mm i.d.) for clean-up and column II (Inertsil ODS-80A column, 5 microm, 150 mm x 4.6mm i.d.) for separation. The mobile phase consisted of phosphate buffer-acetonitrile (92:8 v/v, pH 7.0) for clean-up and phosphate buffer-acetonitrile-methanol (65:30:5 v/v/v, pH 6.5) for separation, respectively. The peak was detected with an ultraviolet detector set at a wavelength of 302 nm, and total time for chromatographic separation was approximately 25 min. The validated concentration ranges of this method were 3-2000 ng/ml for omeprazole, 3-50 ng/ml for 5-hydroxyomeprazole and 3-1000 ng/ml for omeprazole sulfone. Mean recoveries were 84.3% for omeprazole, 64.3% for 5-hydroxyomeprazole and 86.1% for omeprazole sulfone. Intra- and inter-day coefficient variations were less than 5.1 and 6.6% for omeprazole, 4.6 and 5.0% for 5-hydroxyomeprazole and 4.6 and 4.9% for omeprazole sulfone at the different concentrations. The limits of quantification were 3 ng/ml for omeprazole and its metabolites. This method was suitable for use in pharmacokinetic studies in human volunteers, and provides a useful tool for measuring CYP2C19 activity.Journal of Chromatography B 04/2006; 832(2):241-8. DOI:10.1016/j.jchromb.2006.01.022 · 2.69 Impact Factor