Implications of Peroxide Formation in Lotion and Ointment Dosage Forms Containing Polyethylene Glycols

The influence of various factors on the formation rate of peroxide-like impurities in polyethylene glycols was studied. Conditions of high temperature and agitation increased this rate. Varying formation rates were found with glycols from different manufacturers and this seemed to be related to the initial level of peroxide impurity. Aged samples generated peroxides at a faster rate than glycols recently acquired from a manufacturer. Peroxides were an intermediata in the degradation of glycols to carboxylic acids. It is suggested that an atmosphere of nitrogen be used when solubilizing drugs in glycols at high temperatures. The mixing of polyethylene glycol 1500 at 70° with white petrolatum, resulted in a rapid decrease in peroxide content in the glycol and improved the stability of oxidizable drugs in ointment formulations containing glycol and petrolatum.