Simultaneous determination of rabeprazole enantiomers and their four metabolites after intravenous administration in beagle dogs by a stereoselective HPLC-MS/MS method and its application in pharmacokinetic studies

Abstract

A sensitive, rapid and stable HPLC-MS/MS method has been developed and validated for the determination of rabeprazole enantiomers and their four metabolites, namely rabeprazole thioether, rabeprazole sulfone and desmethyl rabeprazole enantiomers, in beagle dog plasma using esomeprazole as the internal standard. The analytes and the internal standard were extracted from plasma samples by liquid–liquid extraction and separated on a Chiral-HSA column using acetonitrile-10 mmol L⁻¹ ammonium acetate as the mobile phase by gradient elution. The method was validated with respect to sensitivity, specificity, linearity, precision, accuracy and especially the stability of analytes under various conditions, and was successfully applied in evaluating the pharmacokinetic profiles of racemic rabeprazole, the pure enantiomers and their metabolites in beagle dogs after single intravenous administration of (R)-rabeprazole sodium injection (at 0.33, 1 and 3 mg kg⁻¹), (S)-rabeprazole sodium injection (at 1 mg kg⁻¹) and racemic rabeprazole sodium injection (at 2 mg kg⁻¹). The two enantiomers showed different profiles of pharmacokinetic parameters. The AUC_0–t and t_1/2 values of (R)-rabeprazole were higher and the clearance (CL) value of (R)-rabeprazole was lower than that of (S)-rabeprazole. Compared to (S)-rabeprazole, the higher absorption and slower elimination of (R)-rabeprazole explain why (R)-rabeprazole is more effective than the racemate.