The influence of ageing on the release of hydrocortisone from o/w creams

The influence of ageing on the release of hydrocortisone from o/w creams containing ionic and nonionic emulgators and different amounts of water was investigated over a period of 48 weeks. The influence of ageing was dependent on the type of emulgator and the amount of water in the cream. Up to 12 weeks of storage, ageing affected the creams containing ionic emulgators by retarding the release of hydrocortisone; after that, hydrocortisone release was enhanced and the release profile also changed. For the creams containing 60% water, the effects of ageing differed slightly from the creams containing 40% or 80% water. These findings can be explained by particle growth and agglomeration but changes in the microstructure of the creams may also be important. Creams containing nonionic emulgators were only slightly affected by ageing.