Influence of ageing on hydrocortisone particles in o/w creams

The influence of ageing on hydrocortisone crystal growth and particle location in nine o/w-creams was examined microscopically over a period of 48 weeks. The creams consisted of ionic or non-ionic surfactants as emulgators, contained different amounts of water, and had a hydrocortisone concentration of 1%. In the dispersed state, the hydrocortisone particles were found to migrate to the liquid paraffin-water interface, in some cases covering the whole oil droplet in the cream. During storage the hydrocortisone particles also grew slightly larger. These enlarged hydrocortisone particles tended to lie parallel to each other. The location of hydrocortisone particles at the liquid paraffin-water interface can be discussed in terms of attainment of the minimum free energy state.