Stability of Hydrocortisone in Polyethylene Glycol Ointment Base

Abstract

The degradation of 1% hydrocortisone in polyethylene glycol ointment USP was investigated. The stability tests were conducted on two different batches of ointments at 23, 45, and 60o for about 4months. Decomposition occurred at the C-17 side chain as assayed by the blue tetrazolium reaction, as well as in ring A as determined by UV spectroscopy. The decomposition of the C-17 side chain was much faster (average half-life of 186days at 60o) as compared with ring A (average half-life of 505days at 60o). Decomposition of the C-17 chain appeared to be first order but was zero order for ring A. The energy of activation was determined to be 9.7 kcal/mole. Based on these studies, the shelflife for a 1% hydrocortisone ointment in polyethylene glycol base is suggested to be about 6months. The shelflife may be extended to about 9months with the addition of a 5% excess of the active ingredient at the time of manufacture.