Up‐scheduling and codeine supply in Australia: analysing the intervention and outliers

Background and aims Over‐the‐counter codeine products were up‐scheduled to prescription only in Australia from February 2018. This trend study aimed to identify changes in codeine supply before and after the February 2018 implementation. Design, setting and cases Time–series regression analysis of monthly medicine supplies in Australia from 2014 to 2018. The February 2018 up‐scheduling was pre‐specified as the intervention; outlier analysis was used to detect automatically sudden unexpected changes before February 2018. Measurements Per‐capita supplies based on national data for pharmaceutical wholesales and population exposure. Weight of supplies in milligrams for low‐dose codeine (≤ 15 mg per tablet or ≤ 1.92 mg per ml, originally sold over the counter but up‐scheduled after February 2018), high‐dose combination codeine (30 mg per tablet, prescription only throughout the study period) and all codeine. Findings Several level shifts in supply occurred during the 5 years, led by one of −4.4% [95% confidence interval (CI) = −6.6 to −2.1%] in high‐dose codeine in 2015, followed by shifts in low‐dose codeine of −40.0% (CI = −46.9 to −32.3%) and −82.2% (CI = −84.3 to −79.9%), respectively, before and after February 2018. High‐dose codeine supply increased by 4.4% (CI = 1.8–7.1%) immediately after up‐scheduling. Also detected were transient increases and decreases in 2016 and 2017. Compared with pre‐2015 levels, the February 2018 up‐scheduling was associated with reductions of 45.7% (CI = 43.2–48.0%) and 89.3% (CI = 87.9–90.6%), respectively, in all and low‐dose codeine supply but no change in high‐dose codeine supply. The level shifts and transient changes were located around various regulatory activities, including public announcements and expert advisory meetings on up‐scheduling. Conclusion Up‐scheduling of over‐the‐counter codeine products in Australia in 2018 appears to have been associated with a near halving of Australia's national codeine supply. The transition occurred in multiple forms and phases.