Objective To compare the risk of mortality among people with opioid use disorder on and off opioid agonist treatment (OAT) in a setting with a high prevalence of illicitly manufactured fentanyl and other potent synthetic opioids in the illicit drug supply. Design Population based retrospective cohort study. Setting Individual level linkage of five health administrative datasets capturing drug dispensations, hospital admissions, physician billing records, ambulatory care reports, and deaths in British Columbia, Canada. Participants 55 347 people with opioid use disorder who received OAT between 1 January 1996 and 30 September 2018. Main outcome measures All cause and cause specific crude mortality rates (per 1000 person years) to determine absolute risk of mortality and all cause age and sex standardised mortality ratios to determine relative risk of mortality compared with the general population. Mortality risk was calculated according to treatment status (on OAT, off OAT), time since starting and stopping treatment (1, 2, 3-4, 5-12, >12 weeks), and medication type (methadone, buprenorphine/naloxone). Adjusted risk ratios compared the relative risk of mortality on and off OAT over time as fentanyl became more prevalent in the illicit drug supply. Results 7030 (12.7%) of 55 347 OAT recipients died during follow-up. The all cause standardised mortality ratio was substantially lower on OAT (4.6, 95% confidence interval 4.4 to 4.8) than off OAT (9.7, 9.5 to 10.0). In a period of increasing prevalence of fentanyl, the relative risk of mortality off OAT was 2.1 (95% confidence interval 1.8 to 2.4) times higher than on OAT before the introduction of fentanyl, increasing to 3.4 (2.8 to 4.3) at the end of the study period (65% increase in relative risk). Conclusions Retention on OAT is associated with substantial reductions in the risk of mortality for people with opioid use disorder. The protective effect of OAT on mortality increased as fentanyl and other synthetic opioids became common in the illicit drug supply, whereas the risk of mortality remained high off OAT. As fentanyl becomes more widespread globally, these findings highlight the importance of interventions that improve retention on opioid agonist treatment and prevent recipients from stopping treatment.

Formatted for AddictionThe cascade of care for opioid use disorder: a retrospective study in

OBJECTIVES Evidence on the perinatal health of mother-infant dyads affected by opioids is limited. Elevated risks of opioid-related harms for people with opioid use disorder (OUD) increase the urgency to identify protective factors for mothers and infants. Our objectives were to determine perinatal outcomes after an OUD diagnosis and associations between opioid agonist treatment and birth outcomes. METHODS We conducted a population-based retrospective study among all women with diagnosed OUD before delivery and within the puerperium period in British Columbia, Canada, between 2000 and 2019 from provincial health administrative data. Controlling for demographic and clinical characteristics, we determined associations of opioid agonist treatment on birth weight, gestational age, infant disorders related to gestational age and birth weight, and neonatal abstinence syndrome via logistic regression. RESULTS The population included 4574 women and 6720 live births. Incidence of perinatal OUD increased from 166 in 2000 to 513 in 2019. Compared with discontinuing opioid agonist treatment during pregnancy, continuous opioid agonist treatment reduced odds of preterm birth (adjusted odds ratio: 0.6; 95% confidence interval: 0.4–0.8) and low birth weight (adjusted odds ratio: 0.4; 95% confidence interval: 0.2–0.7). Treatment with buprenorphine-naloxone (compared with methadone) reduced odds of each outcome including neonatal abstinence syndrome (adjusted odds ratio: 0.6; 95% confidence interval: 0.4–0.9). CONCLUSIONS Perinatal OUD in British Columbia tripled in incidence over a 20-year period. Sustained opioid agonist treatment during pregnancy reduced the risk of adverse birth outcomes, highlighting the need for expanded services, including opioid agonist treatment to support mothers and infants.

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