Stability of Oxycodone Solutions Containing S-Ketamine or Dexmedetomidine

ObjectivesTo determine whether adding S-ketamine or dexmedetomidine to oxycodone affects the microbiological, physical, or chemical stability of patient-controlled analgesia (PCA) solutions prepared in a hospital pharmacy. MethodsOxycodone solution (1 mg/mL) and three oxycodone-S-ketamine mixtures (0.25, 0.50, 0.75 mg/mL) and three oxycodone-dexmedetomidine mixtures (2.5, 5.0, 10 {micro}g/mL) were compounded under validated EU GMP Class A/B aseptic conditions and filled into PCA reservoirs. Reservoirs (n=42 for physicochemical studies; n=21 for sterility; n=4 for antimicrobial activity testing) were stored at 2-8{degrees}C for 28 days, then at 20-25{degrees}C for 2 days. Sterility was assessed by membrane filtration according to Ph. Eur. 2.6.1. Physical stability was evaluated by visual inspection, pH, weight, and osmolality. Chemical stability was assessed using a validated HPLC-UV method developed in accordance with FDA and ICH Q2(R1) guidelines. ResultsAll antimicrobial activity tests showed growth of the six reference strains, indicating no inhibition by the drug mixtures. All 21 sterility-test reservoirs remained free of turbidity throughout 30 days. No visual changes, precipitation, or discolouration were observed. Weight loss was [&le;]0.3%, pH changes were between required range 4,5-7, and osmolality increased by <1.4% during the study. Measured oxycodone, S-ketamine, and dexmedetomidine concentrations remained within {+/-}5% of initial values, and no degradation products were detected. ConclusionsOxycodone PCA solutions containing S-ketamine or dexmedetomidine remained sterile, physically stable, and chemically stable for 28 days at 2-8{degrees}C followed by 2 days at room temperature at 20-25{degrees}C. These findings support extended shelf-life and centralized batch preparation of opioid-adjuvant PCA reservoirs in hospital pharmacy practice. Key MessagesO_ST_ABSWhat is already known on this topicC_ST_ABSOpioid-adjuvant combinations such as oxycodone with S-ketamine or dexmedetomidine are increasingly used in patient-controlled analgesia, but no commercial multi-agent formulations exist. Hospital pharmacies therefore prepare these mixtures as compounded sterile preparations, despite limited data on their chemical and microbiological stability. What this study addsThis study demonstrates that oxycodone PCA solutions containing S-ketamine or dexmedetomidine remain chemically stable and microbiologically sterile for 28 days at 2-8{degrees}C plus 2 days at 20-25{degrees}C, when prepared under validated aseptic conditions. Concentrations of all analytes remained within {+/-}5% of initial values, and no degradation products were detected using a validated HPLC-UV method. How this study might affect research, practice or policyThese stability data support the assignment of extended beyond-use dates and enable centralized batch compounding of PCA reservoirs in hospital pharmacies. The findings have the potential to reduce aseptic workload, improve production efficiency and decrease medication waste while ensuring product quality.