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

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-beta-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 (k(obs)), 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.