Changing patterns of opioid agonist therapy prescribing in a network of specialised clinics providing care to people with opioid use disorder in Victoria, Australia, 2015 to 2023.

Introduction: Long-acting injectable buprenorphine (LAIB) reduces the frequency of contact with opioid agonist therapy (OAT) service providers. Limited data exist on OAT prescribing in Australia after the introduction of subsidised LAIB prescribing in September 2019. This ecological study describes trends in OAT prescribing between 2015 and 2023 across a network of primary care services in Victoria, Australia.

Methods: We utilised electronic medical records from 17 clinics in Victoria that provide services to people with opioid dependence to describe OAT prescribing patterns. We described the annual number and type (methadone, buprenorphine, LAIB) of OAT prescriptions issued, individuals prescribed, and individuals initiating OAT. Interrupted time series assessed changes in quarterly OAT prescribing following the introduction of LAIB.

Results: Between 2015 and 2023, the average annual number of OAT prescriptions issued, and the average number of recipients prescribed OAT were 47,648 and 6470, respectively. Between 2020 and 2023, the proportion of individuals initiating on LAIB increased from 7% (73/1078) to 31% (357/1146). There was increasing quarterly OAT prescribing before the introduction of LAIB, after which methadone and buprenorphine prescribing declined by 2.6% (CR 0.974; 95% CI 0.968-0.980) and 3.2% (CR 0.968; 95% CI 0.963-0.973), respectively. After being introduced, quarterly LAIB prescribing increased by 13.1% (CR 1.131; 95% CI 1.096-1.167).

Discussion and conclusions: We found substantial changes in OAT prescribing patterns in Victoria between 2015 and 2023, with shifts away from oral methadone and sublingual buprenorphine to LAIB. Alongside ongoing monitoring of prescribing patterns, future research should assess how LAIB impacts patient health and social outcomes.