Previous reports indicate that pharmacists are assigning a wide variety of beyond-use dates to extemporaneously compounded medications in topical Pluronic lecithin organogel. The objective of this study was to evaluate the stability of promethazine in Pluronic lecithin organogel over a period of six months and to determine an appropriate beyond-use date. A stability-indicating high-performance liquid chromatography method for promethazine in Pluronic lecithin organogel was validated in our laboratory. Samples of each formulation were analyzed by high- performance liquid chromatography at 0, 7, 14, 21, 28, 45, 60, 90, and 180 days. At each time point, the average concentration and average percent of initial concentration were calculated. The beyond-use date was determined at the time period that the samples were physically stable and maintained at least 90% of the initial concentration. Promethazine hydrochloride was chemically stable in Pluronic lecithin organogel for the period of six months. However, the formulation was physically stable only up to 60 days, and the gel matrix showed signs of physical instability at 90 days, therefore, a 60-day beyond-use date is appropriate for this formulation.