Objectives The study evaluated the stability of three combinations of oxycodone and ketamine diluted in normal saline (NS) after storage for 7 days at 23°C and exposed to light. Methods : The stability of three mixtures of oxycodone and ketamine (oxycodone 0.4 mg/mL+ketamine 40 mg/mL, oxycodone 10 mg/mL+ketamine 0.1 mg/mL and oxycodone 10 mg/mL+ketamine 40 mg/mL) in NS stored in a polypropylene syringe and a polyvinyl chloride (PVC) bag was studied. The physical characteristics, including pH, colour and precipitation, were evaluated. The samples were analysed in triplicate by a stability-indicating high-performance liquid chromatography method. Results : There was no significant change in the pH values of any solution. No precipitation or change in colour was observed. All formulations maintained more than 95% of the initial concentration of each drug on day 7. No trace of degradation products was detected. Conclusions : Ketamine (0.1–40 mg/mL) combined with oxycodone (0.4–10 mg/mL) is physically compatible and chemically stable for 7 days when diluted with NS, packaged in polypropylene syringe or PVC bag and stored at 23°C.