Degradation kinetics of mometasone furoate in aqueous systems.

Mometasone furoate (MF) is a synthetic glucocorticoid. There is little information available on the stability of MF and no degradation products have been unequivocally identified. Thus, the primary objective of this study was to characterize the degradation of MF, qualitatively and quantitatively. Stability of MF decreased with increasing pH (>4) and decreasing ionic strength in aqueous media. The chemical stability of MF in aqueous systems was significantly dependent on pH. MF appeared to be stable at pH < 4 but degraded to four products at higher pH. The degradation of MF in aqueous solutions follows pseudo-first-order kinetics and involved a series of parallel and consecutive reactions. The turnover of MF and its products appears to be catalyzed by the hydroxide ion. The pH dependence of these reactions should be considered, when formulating or extemporaneously compounding MF formulations. An optimal pH of stability was below pH 4. The changes in pH, however, do not appear to be the only factor of importance, since an increase in ionic strength and buffer concentration displayed a stabilizing effect on this glucocorticoid in the buffers tested. Trace metal ions are unlikely to be involved in degradation of MF in aqueous solution.