Protocol for a multicentre randomised controlled trial of the Pharmacy Homeless Outreach Engagement Non-medical and Independent Prescriber (PHOENIx) intervention for people facing severe and multiple disadvantages.

INTRODUCTION: People experiencing severe and multiple disadvantage (SMD: homelessness, substance use and criminal offending) have multiple intersecting unmet health and social care needs and high mortality rates, often due to street-drug overdose. Pilot randomised controlled trials (RCTs) suggest an integrated, holistic, collaborative outreach intervention (Pharmacy Homeless Outreach Engagement Non-medical Independent Prescribing Rx (PHOENIx)) involving generalist-trained pharmacists, nurses or General Practitioners accompanied by staff from third sector homeless organisations may improve outcomes, including reducing overdose.

METHODS: Multicentre, parallel group, prospective RCT with parallel economic and process evaluation. Set in six areas of Scotland, UK, 378 adults with SMD will be recruited and randomised (stratified by setting and previous non-fatal overdoses) to PHOENIx intervention in addition to usual care (UC) or UC. Aiming to meet participants weekly for 9-15 months, PHOENIx teams assess and address health and social care needs while referring onwards as necessary, co-ordinating care with wider health and third sector teams. During a person-centred consultation, in the participants' choice of venue, and taking account of the participant's priorities, the NHS clinician may prescribe, de-prescribe and treat, for example, wound care, and refer to other health services as necessary. The third sector worker may help with welfare benefit applications, social prescribing or advocacy, for example, securing stable housing. Pairings of clinicians and third sector workers support the same participants. The primary outcome is time to first fatal/non-fatal street-drug overdose at nine months. Secondary endpoints include health-related quality of life, healthcare use and criminal justice encounters. A health economic evaluation will assess cost per quality adjusted life year of PHOENIx relative to standard care. A parallel qualitative process evaluation will explore the perceptions and experiences of PHOENIx, by participants, stakeholders and PHOENIx staff.

ANALYSIS: The primary and other time-to-event secondary outcomes will be analysed by Cox proportional hazards regression.

ETHICS AND DISSEMINATION: IRAS number 345246, approved 23/10/2024 by North of Scotland Research Ethics Service. Results will be shared with participants, third sector homelessness organisations, health and social care partnerships, then peer-reviewed journals and conferences worldwide, from the first quarter of 2027.

TRIAL REGISTRATION NUMBER: ISRCTN12234059 registered on 20/2/2025 (ISRCTN).