Non-medical use of pharmaceutical opioids with and without other illicit substance use: Trends from two repeated nationally representative Australian surveys.

Background: Due to concerns over the public health impact of increasing opioid use, Australia up-scheduled codeine in 2018, requiring codeine-containing pharmaceuticals to be prescription-only. We examined pre-post changes in the prevalence and correlates of non-medical use of pharmaceutical opioids (NMUPO) and other illicit substance use (ISU).

Methods: We conducted a cross-sectional analysis of 45,463 participants aged 14 or above in the Australian National Drug Strategy Household Surveys (NDSHS) 2016 and 2019. Participants were categorized based on their past 12 months NMUPO and ISU patterns. Correlates examined included socio-demographic, psychological (Kessler 10), health and behavioral variables.

Results: The overall prevalence of any NMUPO decreased from 3.56% in 2016 to 2.65% in 2019, and the prevalence of codeine use from 2.98% to 1.49%. No significant changes were observed in the use of other types of painkillers (e.g. oxycodone and fentanyl) between 2016 and 2019. The overall decrease in NMUPO primarily occurred among people who used NMUPO only and did not use other illicit drugs. Older adults were more likely to report NMUPO only. Younger age, higher psychological distress, risky alcohol use, and daily smoking were associated with both NMUPO and illicit drug use.

Conclusions: A comparison of cross-sectional data from two time-points showed that the prevalence of NMUPO use among people who used NMUPO exclusively was lower post-up-scheduling of codeine in Australia. However, NMUPO use did not reduce among people who used both NMUPO and other illicit drugs. Public health interventions are needed to reduce opioid-related harm in those who also used other illicit drugs.