BACKGROUND/AIMS: Take-home naloxone (THN) programmes have been introduced in many European countries to provide non-medically trained people who are likely to witness an opioid overdose, including people who use opioids, with a naloxone kit and training. This study used data obtained from people supplied with THN and systematically followed up for 6 months to determine the proportion witnessing an overdose, administering naloxone and successfully reversing opioid overdose in real-world settings. The study aimed to compare reports of witnessed opioid overdose between participants in treatment and not in treatment at the time of recruitment.

DESIGN: A multi-country, observational prospective cohort study. Participants supplied with THN were asked to report any witnessed overdose events and participate in a systematic follow-up over a 6-month period.

SETTING: Participants were recruited from THN programmes at 22 drug treatment and harm reduction services in England, Wales, Scotland and Sweden.

PARTICIPANTS: A total of 1025 people who used opioids and who were supplied with THN were recruited between June 2021 and November 2023, of whom 594 (58%) were successfully followed at 6 months. The participants were predominantly men (75%) and white (80%), with a mean age of 45.5 years (standard deviation 10).

MEASUREMENT: Main outcomes: whether or not THN was administered at a witnessed overdose and overdose outcome where THN administered. Accurate recognition of opioid overdose, availability of naloxone and appropriate responses (including administering naloxone) to an opioid overdose were captured. Outcomes were compared between participants in treatment and not in treatment.

FINDINGS: Of the 594 followed over 6 months, 160 (27%) witnessed at least one overdose. The likelihood of witnessing an overdose was higher among participants not in treatment than participants in treatment [56% vs. 23%; odds ratio = 4.4; 95% confidence interval (CI) = 2.69-7.21; P = 0.001]. THN was administered at most witnessed overdose events (83%; 95% CI = 74-85). Seven deaths were reported (4.4%; 95% CI = 0.02-8.8) by participants to be due to an overdose. For five deaths, naloxone was administered but was believed by participants to have been administered after death. Ninety-five percent (152) of participants were able to recognise one or more critical signs of overdose and respond appropriately. When naloxone was available, it was administered in almost all (90%; 142) emergency situations.

CONCLUSIONS: In the United Kingdom and Sweden, people who use opioids appear to be likely to witness and recognise an opioid overdose, be the only person carrying naloxone at the overdose and be both willing and able to safely and effectively administer naloxone in a timely response. Clinical trial registration details (if applicable): ClinicalTrials.gov Identifier: NCT05072249. Date of Registration: 8.10.2021.