Effect of elevated temperature and light on the stability of butorphanol tartrate

The purpose of this investigation was to determine the short-term stability of butorphanol tartrate in presence of diluents. A 10-mg/mL solution of butorphanol tartrate was diluted to 5 mg/mL using normal saline, 5% dextrose in water (D5W), or sterile water for injection. The diluted solutions were divided into two groups. The effect of temperature was tested by placing one group of sealed amber vials at room temperature and at 37 degrees C. The effect of light was studied by placing a second group in amber and clear vials, then exposing them directly to light. At regular time intervals over a period of 5 weeks, the solutions were analyzed for butorphanol tartrate and degradation products using a high-performance liquid chromatography assay. The concentration of butorphanol tartrate remained practically unchanged, indicating that butorphanol tartrate is not affected by heat or light in the presence of any of the diluents over a period of 5 weeks.