Evaluation of the stability of acetaminophen in pluronic lecithin organogel and the determination of an appropriate beyond-use date.

Fluoxetine is a commonly prescribed psychotropic medication for a variety of behavioral diagnoses in veterinary practice, and fluoxetine in Pluronic lecithin organogel has been used successfully in treating inappropriate urine spraying in felines. Historically, pharmacists have assigned a variety of beyond-use dates to extemporaneously compound drugs in Pluronic lecithin organogel. The objective of this study was to evaluate the stability of fluoxetine 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 fluoxetine in Pluronic lecithin organogel was validated in our laboratory. Fluoxetine-Pluronic lecithin organogel 50 mg/mL was prepared by a local compounding pharmacy and analyzed by high-performance liquid chromatograph at 0, 7, 14, 21, 28, 45, 60, 90, and 180 days. Physical stability was also assessed by visual observation. At each time point percent of initial concentration was calculated. The beyond-use date was determined as the time period that the samples maintained at least 90 percent of the initial concentration. At 180 days, the mean percent of initial concentration was 99 +/- 1.5 and, visually, the fluoxetine-Pluronic lecithin organogel retained the original color and consistency, without detectable separation of the different phases of Pluronic lecithin organogel. Since fluoxetine was physically stable and retained greater than 90 percent of initial concentration in Pluronic lecithin organogel for 180 days when stored at room temperature and protected from light, a beyond-use date of 180 days is appropriate.