New Trial Protocol Tests Collaborative Care for Polysubstance Use

Most people with moderate to severe substance use disorder do not use a single drug. They combine opioids, stimulants and alcohol, a pattern the authors of a newly published trial protocol call the predominant form of the condition — and one the treatment evidence base was never built to address, because the trials that established medications for opioid use disorder, medications for alcohol use disorder and contingency management for stimulants each studied one substance at a time.

The CoCare trial, short for Collaborative Care for Polysubstance Use in Primary Care Settings, is designed around that gap. Its protocol appeared Thursday in Addiction Science & Clinical Practice, with Jane M. Liebschutz and 18 co-authors describing a cluster-randomized controlled trial registered at ClinicalTrials.gov as NCT06116266.

Randomizing doctors, not patients

CoCare randomizes at the level of the primary care provider rather than the individual patient, so entire provider panels are assigned either to the collaborative care intervention or to enhanced usual care. The trial runs across six distinct geographic sites.

Eligible patients are adults in primary care with moderate to severe opioid, stimulant or alcohol use disorder who report using at least two of those substance classes. The trial's rationale rests on where those patients already are: a minority of people with active polysubstance use disorder seek specialty addiction treatment, the protocol notes, but many of them see a primary care clinician regularly.

Four roles around one patient

The intervention assembles a team that does not normally exist in a family medicine practice. A nurse care manager embedded in the practice manages medication-assisted treatment for opioid and alcohol use disorder, runs contingency management, links patients to mental health and addiction treatment, and handles general care management. The patient's own primary care provider prescribes the medications and manages medical conditions.

A remote health coach delivers patient-centered counseling, motivational enhancement and cognitive behavioral therapy, so the talk-based part of the intervention arrives from outside the practice rather than from a clinician with a full schedule. An addiction specialist then advises the nurse care manager and the coach, using population health management tools to decide where to concentrate attention across the panel.

The arrangement is an attempt to solve an access problem with staffing rather than with new clinics. Instead of asking a primary care doctor to become an addiction specialist, CoCare borrows the specialist's judgment through the nurse and the coach, in the setting where patients already show up. If it works, the model fits the existing standard outpatient infrastructure rather than requiring a new level of care.

What the trial counts

The primary outcome is deliberately practical: the total number of self-reported days of opioid use, stimulant use and heavy alcohol use, summed over months four through six of the intervention. Heavy drinking is defined as four or more drinks per day for women and five or more for men.

Outcomes are assessed monthly through text-message surveys using items drawn from the Addiction Severity Index, and the primary analysis uses a mixed-effects negative binomial model with a log link, a specification suited to count data such as days of use. Secondary outcomes extend beyond substance use itself.

That measurement choice matters for how the results should be read when they arrive. Self-reported days of use over a six-month window is a substance-use endpoint, not a mortality or overdose endpoint, and it will not settle whether collaborative care reduces deaths. It will show whether a team-based model can move a population that single-substance trials have largely excluded, which is the question the field has been slow to test.

Why polysubstance use keeps getting studied sideways

The protocol's background section lays out the mismatch plainly. Medications for opioid use disorder and for alcohol use disorder, and contingency management for stimulant use disorder, each carry evidence from trials that rarely enrolled people using multiple substances. Clinicians treating polysubstance use have therefore been extrapolating, combining interventions that were validated separately and hoping the combination holds.

Recent epidemiology has made that extrapolation harder to ignore. A review published this week on concurrent methamphetamine and fentanyl use, covered here, described how the two drugs now appear together in the same supply and often in the same person, with outcomes worse than either alone. CoCare's authors make the same point in clinical terms: polysubstance use is associated with higher mortality, more morbidity and poorer treatment response.

The trial has not reported outcome data. What the protocol establishes is a testable structure — six sites, four roles, one shared outcome measure — for a question that has mostly been answered by assumption.