Influence of sulfobutylether-β-cyclodextrin on the stability of S- and R- omeprazole

Abstract

Omeprazole (OME), a proton pump inhibitor used to treat acid reflux disease and gastric ulcers presents a formulation challenge due to its rapid decomposition at acidic and neutral pHs. Thus, the aim of this project was to investigate whether interaction with sulfobutylether-β-cyclodextrin (Captisol®-CD) could improve omeprazole stability and provide more efficient oral liquid formulations.

A stability-indicating high performance liquid chromatography assay allowed for the quantitation of S- and R-forms of OME in the presence and absence of Captisol®-CD. The developed method was validated to discriminate between OME and its degradation products and used to describe the kinetic model of OME at different pH values over a period of 36 days.

Calculated degradation constants (kobs), were directly correlated with the H+ concentrations of the solutions regardless of whether the omeprazole was complexed with the Captisol®-CD or not. Moreover, the pH-rate profile curve indicated that in all cases, maximum stability was achieved at pH 11. Though it was anticipated that interaction of OME with Captisol®-CD might increase the relative stability of OME at a lower pH, the cavity of the cyclodextrin was too small to allow the inclusion to occur. However the R-isomer of OME, both in the presence or absence of the cyclodextrin appeared to be slightly less stable than the corresponding S-form at the same pH conditions.