A prospective cohort study evaluating the impact of upscheduling codeine in Australia among frequent users of codeine

Aim: To evaluate and document the impacts of re-scheduling codeine to a prescription-only medication in Australia in February 2018. Design: Prospective cohort study. Participants completed an on-line survey with a range of outcome measures at four time-points, once before codeine was re-scheduled (November 2017) and three times after the event: 1 month after (February 2018), 4 months after (June 2018) and 12 months after (February 2019). Setting: Australia. Participants: Participants were 260 Australians aged 18 years and above who reported regular over-the-counter (OTC) codeine use and, at the time of the study, were not engaged in treatment for codeine dependence. Measurements: Survey measures included estimates of daily average codeine use (mg) and overall daily average opioid use [calculated using an oral morphine equivalent daily dose (OMEDD, mg)], opioid use disorder with regard to codeine use (using a modified Alcohol Use Disorder and Associated Disabilities Interview Schedule-IV), pain and pain self-efficacy, anxiety and depression and health service use. Findings: A reduction in total daily codeine use (mg) from 64.3 mg [95% confidence interval (CI) = 46.7–81.9] in November 2017 (baseline) to 27.6 mg (95% CI = 19.2–36.0) in February 2019 (final time-point) was observed. A decline in the proportion of participants who met criteria for an opioid use disorder was also evident, with 51.2% (n = 133) at baseline relative to 33.3% (n = 58) at the 12-month follow-up. This study had an overall participant retention rate of 67% at the final time-point. Conclusion: Re-scheduling codeine in Australia has been accompanied by significant reductions in codeine use and prevalence rates of opioid use disorder in a cohort of individuals who regularly use the medication, without apparent adverse impacts on pain or measures of anxiety and depression.