Participants
Participant eligibility criteria are described in Table Trial inclusion and exclusion criteriaHomeless (living in temporary accommodation, no fixed abode or rough sleeping) [andAged 18 years or overandOne or more non-prescribed drug overdoses in past 6 months confirmed by self-report and witnessed overdose/ambulance call out/emergency department (ED) visit/naloxone useLiving in residential or community-based rehabilitation facility which has direct access to in-house medical and nursing careorUnable to give written informed consent