Effect of vehicles and other active ingredients on stability of hydrocortisone.

The stability of hydrocortisone in various types of vehicles, aqueous, water-washable (polyethylene glycol ointment base), and oil in water or water in oil-type emulsified vehicles, and in the presence of other ingredients, iodochlorhydroxyquin, menthol, and phenol, was studied under normal conditions (room temperature and weakly acidic pH). The study was conducted using a stability-indicating assay method, high-pressure liquid chromatography. The hydrocortisone was very unstable in water and water-washable ointment base. The addition of alcohol and glycerin to water had a stabilizing effect. Under drastic conditions (very acidic or very basic pH), hydrocortisone proved to be unstable only on the basic side. The data at higher temperatures confirmed that the decomposition in water and polyethylene glycol was pseudo-first order. The decomposition process appears to be different in the highly basic solution versus weakly acidic media or in water versus polyethylene glycol ointment base.