Risk of non-medical drug overdose following prescription of opioids post-injury: A retrospective cohort study.

Background: There has been increasing scrutiny of opioid prescribing following injury because of concerns that prescribed opioids may contribute to addiction and overdose. This study aimed to better understand the relationship between injury, opioids prescribed before and after injury, and non-medical drug poisoning.

Data and methods: Working age (15 to 65 years old) residents of British Columbia's Fraser Health region with an injury that involved an emergency department visit were included. Factors examined included the prescription of opioid and opioid agonist therapy (OAT) medications before and after injury, age, sex, work-related injuries, and socioeconomic status, as well as how they were associated with non-medical drug poisoning risk and post-injury prescriptions.

Results: Opioid-naive individuals (those without an opioid prescription captured before their injury) who were prescribed OAT medication-a marker of opioid use disorder-following their injury had a higher risk of subsequent non-medical drug poisoning (Hazard ratio (HR): 21.4 to 22.4 compared with opioid-naive individuals without an opioid or OAT prescription). Post-injury opioid prescription in these individuals increased poisoning risk (HR: 1.27 compared with those without a prescription). Being of male sex (HR: 1.80), being younger (HR: 0.76 for every 10-year increase in age) and living in the lowest-income neighbourhoods (HR: 1.44 compared with the middle quintile) increased poisoning risk. Compared with injuries sustained outside of work, work-related injuries reduced risk (HR: 0.62).

Interpretation: Among a cohort of British Columbians visiting emergency departments following an injury, opioid prescribing in patients who were opioid-naive appears to be a minor contributor to non-medical drug poisoning, particularly when compared with other patient factors, such as being male, being younger and having a low socioeconomic status.