Application of a liquid chromatographic/tandem mass spectrometric method to a urinary excretion study of rabeprazole and two of its metabolites in healthy human urine

•We develop a LC–MS/MS method for quantification of rabeprazole and its metabolites.•The fully validated assay is applied to urine excretion study of rabeprazole in healthy volunteers.•Rabeprazole stock solutions are stable if dissolved in methanol containing 0.5‰ DEA.•Rabeprazole and its two metabolites undergo nearly non-renal elimination in human. To study urinary excretion properties of rabeprazole and two of its metabolites, i.e. rabeprazole thioether and desmethyl rabeprazole thioether in human urine, a sensitive, selective, accurate and precise method for the quantification of rabeprazole and two of its metabolites using a liquid chromatographic/tandem mass spectrometric method has been developed and validated. Starting with a 200μL urine aliquot, a general sample preparation was performed using protein precipitation with methanol. Analytes were separated on a Dikma Inspire™ C18 column (150mm×2.1mm, 5μm) using a mixture of methanol and aqueous 10mM ammonium acetate buffer containing 0.05% formic acid (55:45, v/v) as mobile phase. Linearity was obtained over the concentration range of 0.1446–96.38ng/mL, 0.3198–319.8ng/mL and 0.05160–82.53ng/mL for rabeprazole, rabeprazole thioether, desmethyl rabeprazole thioether in human urine, respectively. The fully validated method was applied to a urine excretion study of rabeprazole sodium administered as a 30min intravenous infusion for the first time. The calculated cumulative urinary recovery just reached 0.04745‰, 1.272‰ and 0.1631‰ of dose within 24h post-dose for rabeprazole, rabeprazole thioether, and desmethyl rabeprazole thioether, respectively, after intravenous infusion administration, indicating that rabeprazole and its two main metabolites undergo substantial non-renal elimination in healthy Chinese volunteers.