Impact of a policy change restricting access to codeine on prescription opioid-related emergency department presentations: an interrupted time series analysis

Codeine is one of the most commonly used opioid analgesics. Significant codeine-related morbidity and mortality prompted regulatory responses, with the up-scheduling of codeine combination analgesics to prescription-only medicines implemented in Australia in February 2018. This study investigated the impact of codeine up-scheduling on the number of codeine and other (noncodeine) prescription opioid-related emergency department (ED) presentations in a large metropolitan tertiary hospital. Clinical features of these presentations were also examined. Interrupted time series analyses assessed monthly changes in ED presentations from June 2016 to November 2019. In the month immediately after up-scheduling, there was a significant reduction of 3.97 codeine-related presentations (B = -3.97, P = 0.022), indicating a 29.66% level change, followed by a significant change in trend to fewer monthly codeine-related presentations (B = -0.38, P = 0.005). Noncodeine prescription opioid-related (B = -1.90, P = 0.446) and ED presentations overall (B = -118.04, P = 0.140) remained unchanged immediately post-up-scheduling, with a significant change in trend from upward to downward for noncodeine (B = -0.76; P = 0.002) and ED presentations overall (B = -19.34, P = 0.022). A significant reduction of 4.58 (B = -4.58, P = 0.009) in codeine presentations involving subsequent hospital admission immediately post-up-scheduling was found; but no immediate reduction in codeine-related suicide-related overdoses, length of inpatient stay, or re-presentations (P > 0.0125; adjusted for multiple comparisons). Restricting supply of codeine to prescription-only may have resulted in less harmful codeine-related use in the community, without a corresponding immediate decrease in other opioid-related harms.