Long-term Physicochemical Stability of a Pharmaceutical Preparation of Morphine Hydrochloride and Droperidol in Polypropylene Syringes.

Objectives: This study aimed to investigate the physicochemical stability of morphine hydrochloride and droperidol mixture stored in polypropylene syringes to prepare them in advance by a centralised intravenous additive service (CIVAS).

Methods: Five polypropylene syringes containing 2 mg/mL morphine hydrochloride and 0.083 mg/mL droperidol were stored in a light-protected environment at room temperature. The physical and chemical stability of solutions was periodically evaluated over a 50 days-period. The samples were visually and microscopically examined, the absorbance at three different wavelengths (350, 410, and 550 nm) and the pH were measured. An ultra-high performance liquid chromatography-photodiode array detection (UHPLC-PDA) method was developed and validated to determine the concentrations of these two drugs simultaneously.

Results: Over the course of the 50-days evaluation, no observable change in colour, particle or crystal formation was detected in any of the samples by visual and microscopic examinations. The pH and absorbance at only 350 nm exhibited a slight upward trend over time in all five syringes. Regarding the chemical stability, the lower limit of the one-side 95 percent prediction interval (LL95PI) remains above 90% of the initial mean concentration for the five syringes.

Conclusions: The pharmaceutical preparation of 2mg/mL morphine hydrochloride and 0.083 mg/mL droperidol in polypropylene syringes, stored in a light-protected environment at room temperature, displayed stability throughout the 50-days study period. It is noteworthy that even there were slight variations in pH and absorbance at 350 nm, these observations, to the best of our knowledge, do not contraindicate the preparation of this admixture in advance under aseptic conditions by a CIVAS. However, the compounding process must be validated for sterility, accuracy and reproducibility.