Polysubstance use (PSU), particularly opioid-involved and stimulant-involved PSU, is a growing issue in the USA. PSU increases the risk of negative health consequences, including infectious diseases, worsening physical and mental health conditions, and overdose-related deaths. These consequences occur in the context of varying health risk behaviours, substance-related preferences, and treatment engagements among people with PSU. To inform improvements in prevention, harm reduction, and substance use disorder (SUD) treatment, additional research is needed to comprehensively understand the current context and drivers of PSU preferences, motivations, and behaviours.

Herein, we describe the protocol for a prospective cohort study designed to capture detailed patterns, profiles, and trajectories of PSU, with the aim of comprehensively examining the drivers of PSU behaviours and SUD treatment utilisation. Adults (ages 18–75; n=400) who engage in PSU will be recruited from healthcare institutions, an established participant database maintained by an adjacent SUD research team, and online advertisements. Study assessments will capture dynamic patterns, choice preferences, and motivators of PSU via behavioural economic (BE) measures, detailed Timeline Follow-Back (TLFB) interviews, and self-administered surveys. The assessment timeline will include a baseline survey and TLFB interview, weekly TLFB interviews for 4 weeks post-baseline, and follow-up surveys and TLFB interviews at 4-, 8-, and 12-months post-baseline.

The study is funded through the National Institutes of Health Helping to End Addiction Long-term (HEAL) initiative and was approved by the University of Michigan Medical Institutional Review Board. Findings will be disseminated to academic, clinical, and community partners through the Michigan Innovations in Addiction Care through Research and Education programme. Results from this study will inform actionable and practical insights relevant to the delivery of personalised care in the context of PSU.

Excessive opioid prescribing after surgery can lead to adverse events and exacerbate the opioid crisis. Patients undergoing outpatient breast surgery are often prescribed opioids to manage pain at home; however, the value of this approach is uncertain. The Postoperative Analgesia Intervention with Non-opioid Alternatives (PAIN Alt) trial will address the following research question: among patients undergoing outpatient breast surgery, does opioid-free analgesia (OFA) result in non-inferior 7-day pain intensity and pain interference in comparison to opioid analgesia (OA)?

This is a parallel, assessor-blind, open-label randomised trial conducted at seven university-affiliated hospitals in Canada. A sample of 540 adult patients (>18 years) undergoing outpatient mastectomy or lumpectomy will be included. Participants are allocated 1:1 to receive OA (around-the-clock non-opioids and opioids for breakthrough pain) or OFA (around-the-clock non-opioids, with adjustment of non-opioid drugs and/or non-pharmacological interventions for breakthrough pain). The co-primary outcomes are 7-day pain intensity and pain interference (measured using the Brief Pain Inventory). Secondary outcomes include adverse drug events, physical and mental health status, satisfaction with pain management, postoperative complications, chronic pain, opioid misuse, persistent opioid use, healthcare utilisation and costs. The primary statistical analyses will follow the intention-to-treat principle and be conducted using mixed-effects modelling.

This trial is coordinated by the McGill University Health Centre (ethics approval MP-37-2024-102530), with ethics approval being sought at all participating sites. Our results will be published in an open-access, peer-reviewed journal, presented at relevant conferences and disseminated to the public through press releases.

NCT06507345.