To compare the effectiveness of buprenorphine-naloxone (bup/nal) and methadone maintenance therapy (MMT) in the treatment of patients with opioid use disorder (OUD) during the fentanyl era.

Secondary analysis of prospective cohort study data.

Data for the study were collected from 54 clinical sites across Ontario, Canada, between May 2018 and January 2023.

To be included in the present study, participants had to be at least 16 years of age, have provided written informed consent and be receiving either MMT or bup/nal therapy for OUD. This study includes data from 2601 participants, of whom 2068 were receiving MMT and 533 were receiving bup/nal for OUD. The mean age of participants was 39.4 years (SD: 10.9), and 45% were female.

MMT or bup/nal treatment for OUD.

We employed a propensity score matched analysis to compare treatment outcomes among patients receiving MMT compared with bup/nal. We used ongoing illicit opioid use as an indicator of treatment outcome. We considered participants with >50% of urine drug screens in the past 12 months positive for non-prescribed opioids to be ‘non-responders’. We conducted subgroup analyses to identify whether treatment type was associated with ongoing non-prescribed opioid use among patients with and without a history of intravenous drug use (IVDU), and whether treatment type was associated with retention in treatment.

Eight per cent of patients on bup/nal were considered non-responders, compared with 11.9% of patients on MMT. We did not find a statistically significant association between treatment type and treatment response. However, we did find that patients on MMT were more likely to stay in treatment for 12 months (OR 1.79, 95% CI 1.45 to 2.22, p

Among a cohort of patients with OUD receiving treatment during the fentanyl era, we find that there is no statistically significant difference in ongoing non-prescribed opioid use between patients receiving MMT compared with bup/nal. Future studies should aim to further compare treatment effectiveness using patient-centred outcomes and pragmatic trial designs.

Mental health problems are important causes of disability and economic costs worldwide. Randomised clinical trials examining the treatment of mental health disorders measure heterogeneous outcomes, causing difficulties in data synthesis, interpretation and translation into clinical practice. The aim of the Patient Important Outcomes in Psychiatry (PIO-Psych) Initiative is to develop an overarching, transdiagnostic research-based and consensus-based core outcome set for adult mental health disorders.

The development of the PIO-Psych transdiagnostic core outcome set will include three phases: (1) a systematic scoping review of the literature to develop the initial list of outcomes for the Delphi study; (2) a Delphi study in three rounds including people with lived experience of mental health disorders and their relatives, clinicians, researchers and others (administrators, mental healthcare policymakers, philosophers); (3) a hybrid consensus meeting to agree on the final overarching, transdiagnostic core outcome set and corresponding time points of assessment of each outcome.

Ethical approval is not applicable to this study according to the Research Ethics Committee of the Capital Region of Denmark, as it is not an interventional study. All data will be reported anonymously, and it will not be possible to identify study participants. Results will be disseminated via stakeholder and research networks and peer-reviewed publications.

The PIO-Psych Initiative was pre-registered with COMET (Core Outcome Measures for Effectiveness Trials) on 17 May 2024 (https://www.comet-initiative.org/Studies/Details/3125).