Long-Term Physicochemical Stability of a Morphine-Ketamine Admixture in Polypropylene Syringes at Room Temperature

In advance preparation of solutions containing morphine and ketamine can reduce the risk of error, lower costs, and reduce nursing workload, thereby improving the quality of care. However, data on the stability of morphine hydrochloride and ketamine hydrochloride admixture in polypropylene syringes stored at room temperature are lacking.

To assess the physical and chemical stability of a morphine hydrochloride (2.0 mg/mL) and ketamine hydrochloride (3.3 mg/mL) admixture in polypropylene syringes, stored at room temperature and protected from light, for up to 49 days.

Five syringes containing the admixture were prepared under aseptic conditions and analyzed periodically over 49 days. Physical stability was assessed visually, microscopically, and through turbidity measurements. Chemical stability was evaluated using ultra-high-performance liquid chromatography (UHPLC).

No visual precipitation, color change, or significant turbidity increase was observed. The pH remained stable. UHPLC analysis showed that both morphine and ketamine concentrations remained above 90% of initial values at day 49.

The admixture of morphine hydrochloride (2.0 mg/mL) and ketamine hydrochloride (3.3 mg/mL) is physically and chemically stable for at least 49 days in polypropylene syringes stored at room temperature and protected from light. This allows for the in advance preparation of the admixture by centralized intravenous admixture services, improving efficiency and potentially reducing errors.