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

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.

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.

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.

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.

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.