BACKGROUND
In 2019-2020, record-high numbers of overdoses have been reported across the UK. We estimated perceived availability to and carriage of naloxone and explored factors associated with carriage among people who inject drugs (PWID) engaged with services in England, Wales, and Northern Ireland.

METHODS
Participants were PWID enrolled in the Unlinked Anonymous Monitoring Survey in 2019 who reported past-year injection drug use (n = 2,139). Recruitment occurred through specialist and community drug agencies located across the UK, excluding Scotland. Socio-demographic, behavioural and service use characteristics were self-reported. Participants were asked whether they carry naloxone (timeframe unspecified). If they answered "no", they were further asked whether it is available in their area. Perceived naloxone availability and carriage were estimated by requirement region, classified using the Nomenclature of Territorial Units for Statistics 1. We used the Gelberg-Andersen Model of healthcare access to explore predisposing, enabling and need factors associated with regionally-aggregated naloxone carriage.

RESULTS
Perceived naloxone availability was ≥95% in all 11 regions; naloxone carriage varied (mean: 61.1; range: 48%-71%; P<0.01). Among predisposing factors, female gender (adjusted odds ratio (AOR): 1.52; 95% confidence interval (CI): 1.21-1.91) was positively associated with naloxone carriage, whilst recruitment in Yorkshire and the Humber-relative to London-was negatively associated (AOR: 0.55; 95%CI: 0.37-0.82). Among enabling factors, past-year contact with needle and syringe programmes (AOR: 1.74; 95%CI: 1.39-2.18) and currently receiving treatment for drug use (AOR: 1.75; 95%CI: 1.24-2.46) were positively associated with naloxone carriage. Among need characteristics, past-month heroin injection, with or without past-month high-risk drinking or benzodiazepine use, was positively associated with carriage relative to no heroin injection (range of AORs: 1.71-2.58).

CONCLUSION
Perceived naloxone availability is very high among PWID attending services in England, Wales, and Northern Ireland. Naloxone carriage is moderately high and varying across regions, and appears improved through recent engagement with harm-reduction programs.