Introduction Opioid overdose is commonly treated by prehospital emergency services and the majority of the patients are discharged immediately after treatment and a short observation period. There is a minor risk for rebound opioid toxicity and other life-threatening conditions might occur after such episodes. The authors describe the short-term outcome and identify risk factors for death within 48 h after prehospital treatment of opioid overdose in Copenhagen, the capital of Denmark.

Methods Data on all cases of opioid overdose treated by the medical emergency care unit between 1994 and 2003 were recorded prospectively. Risk factors for death within 48 h after initial medical emergency care unit contact were analysed in a multivariable logistic regression analysis.

Results The authors recorded 4762 episodes of opioid overdose, covering 1967 unique identified patients. A total of 78 patients (8.4%, 95% CI 7.0 to 10.4) died within 48 h in the period 1999–2003, and 85% (66/78) of these had cardiac arrest and died. The authors found age >50 years and overdose during the weekend significantly associated with 48-h mortality. Gender, former episodes of opioid overdose, time of the day, month or year were not significantly associated with increased mortality.

Conclusions The author found a 48-hours mortality of 8.4%. Advanced age and opioid overdose in the weekends were significant risk factors. Release on scene after treatment was associated with a very small risk.