Collaborative care for polysubstance use in primary care settings (co-care): protocol for a cluster randomized controlled trial

Background Polysubstance use, the predominant pattern of substance use among individuals with moderate to severe substance use disorder (SUD), confers increased mortality and morbidity risk and worsens clinical treatment outcomes. Despite evidence-based treatment for individual SUDs, including medications for opioid use disorder (OUD) and alcohol use disorder (AUD), and contingency management for stimulant use disorder (StUD), treatment trials rarely address multiple substances. A minority of individuals with active polysubstance use disorder (PSUD) seek specialty addiction treatment but do frequent primary care. The CoCare trial will study the efficacy of a collaborative care intervention to decrease polysubstance use among adult primary care patients with moderate to severe PSUD. Methods The CoCare trial is a cluster-randomized controlled trial, randomized at the level of the PCP, conducted in 6 distinct geographic sites. CoCare tests the efficacy of the CoCare intervention in comparison to enhanced usual care in adult primary care patients with moderate to severe opioid, stimulant and/or alcohol SUD, with concurrent use of at least two of these substance classes. The 6 month Co-Care intervention includes: (1) a practice-embedded nurse care manager (NCM) who manages medications for OUD and AUD, conducts contingency management, links to mental health and addiction treatment, and provides general care management; (2) the patient’s PCP who prescribes medications and manages medical conditions; (3) a remote Health coach who provides patient-centered counseling, motivational enhancement, and cognitive behavioral therapies; and (4) an addiction specialist who advises the NCM and Health Coach on evidence-based patient care using population health management tools. The primary outcome is self-reported days of opioid, stimulant, and heavy alcohol (women 4 + drinks/day, men 5 + drinks/day) use summed over months 4–6. assessed monthly via text messages using items from the Addiction Severity Index. Secondary outcomes include progress in treatment and recovery, substance use frequency and severity, mental health, quality of life, healthcare utilization, overdose risk, pain, and PCP attitudes and behaviors. Analysis of the primary outcome data is based on a mixed-effects negative binomial model with a log link. Discussion Giving the importance of addressing polysubstance use disorder in primary care settings, this trial of collaborative care offers a blueprint for a feasible and effective approach. Trial registration Clinicaltrials.gov, identifier NCT06116266, October 31, 2023.