Compatibility and Stability of Dexamethasone Sodium Phosphate and Ketamine Hydrochloride Subcutaneous Infusions in Polypropylene Syringes

The stability of ketamine hydrochloride injection and dexamethasone sodium phosphate injection, when mixed and stored in polypropylene syringes, was studied. Formulations containing ketamine hydrochloride (50 mg or 600 mg) and dexamethasone sodium phosphate (1 mg) in 0.9% sodium chloride injection (to 14 ml) were prepared and stored at 4°C, 23°C, and 37°C, under normal fluorescent light conditions, for 192 hours. The concentrations of the drugs were determined at 0, 2, 4, 8, 24, 48, 96, and 192 hours using a validated high-pressure liquid chromatography method. The pH, color, and visible particles of each solution were also assessed at each time point. All formulations tested maintained more than 98% of the initial concentrations of both drugs, and no degradation products were detected. The solutions remained clear and colorless and the pH varied within 0.05 units throughout 192 hours. The results indicate that, at the concentrations studied, combinations of ketamine hydrochloride and dexamethasone sodium phosphate in 0.9% sodium chloride injection were physically and chemically stable for at least 192 hours (8 days) when stored in polypropylene syringes.