OBJECTIVE 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.