Stability and Dissolution Rates of Corticosteroids in Polyethylene Glycol Solid Dispersions

A study has been made to examine the stability and dissolution rates of prednisolone, prednisone and hydrocortisone formulated as solid dispersions in polyethylene glycols. Of the five PEG samples used, three enhanced the chemical instability of the steroids; the effect being dependent on the PEG sample and storage conditions of the solid dispersions. Dissolution rates of the steroids were relatively fast from the solid dispersions and showed no significant changes upon storage. Using two methods of analysis (direct UV spectrophotometry and the USP blue tetrazolium method), it is concluded that the chemical instability of the steroids in some PEG samples was due to alterations in the dihydroxy acetone side chain. One of the decomposition products found appeared to be an acidic compound resulting from oxidation of the C₁₇ side chain. The oxidation is presumably accelerated by a peroxide impurity in PEG samples.