Association between type of opioid prescribed postpartum and persistent opioid use: a population-based cohort study

Objectives To examine whether postpartum treatment with oxycodone is associated with an increased risk of new persistent opioid use relative to codeine. Methods Population-based retrospective cohort study of opioid-naive women who gave birth in Ontario, Canada between September 1, 2012 and March 31, 2018. Using linked administrative healthcare databases, women prescribed oxycodone postpartum were compared to those prescribed codeine postpartum. The primary outcome was persistent opioid use at 90 days following the initial postpartum prescription, with codeine as the reference exposure. Persistent use at 90 days was defined as any filled prescription in the 28-days (76-104 days), and 56-days (62-118 days) surrounding the 90-day mark. Relative risks (aRR) were adjusted for maternal, delivery, and prescription characteristics. Results We identified 21,365 postpartum women newly prescribed codeine and 43,767 newly prescribed oxycodone. Compared to codeine, an initial prescription for oxycodone was not associated with persistent opioid use at 90 days, whether a 28-day (aRR 1.12; 95%CI 0.92-1.36) or 56-day (aRR 1.06; 95%CI 0.91-1.24) window around the 90-day outcome was considered. Results were unchanged in a propensity-score matched analysis. A prescription containing greater than 225 milligrams of morphine equivalents was associated with an increased risk of persistent use (aRR 1.87; 95%CI 1.43-2.44), as was an initial prescription duration longer than 7 days (aRR 1.59; 95%CI 1.26-2.03). Conclusions The risk of new, persistent opioid use after delivery was similar for oxycodone and codeine. Limiting the volume and duration of the initial opioid prescription may be important interventions to reduce the risk of persistent opioid use in postpartum women.