Sweden's first Take-Home Naloxone program: participant characteristics, dose endpoints and predictors for overdose reversals.

Background: Opioid overdoses are a growing concern, particularly among people who inject drugs. Sweden, with a comparatively high proportion of drug-related mortality, introduced its first Take-Home Naloxone (THN) program in 2018, at the Stockholm needle and syringe program (NSP). In this study we compare THN participant characteristics regarding refills and overdose reversals as well as investigate predictors associated with number of reversals. We also investigate interventions performed in overdose situations and endpoints for naloxone doses.

Methods: This was a prospective open inclusion cohort study conducted between January 24^th 2018 and March 31^st 2022 at the Stockholm NSP. Participants received THN, free of charge, after a training session and provided data regarding drug use and overdose experiences. During refill visits, participants reported if the naloxone was used for overdose reversal and, if so, responded to a ten-item questionnaire which included stating whether the naloxone recipient was the participant themselves or somebody else. Questionnaire data was combined with NSP database demographic data. Zero-inflated Poisson regression was applied to analyse predictors for number of reported overdose reversals.

Results: Among study participants (n = 1,295), 66.5% stated opioids as their primary drug, and 61.4% and 81.0% had previous experience of a personal or witnessed overdose, respectively. Overall, 44.0% of participants reported a total of 1,625 overdose reversals and the victim was known to have survived in 95.6% of cases. Stimulant use (aIRR 1.26; 95% CI 1.01, 1.58), benzodiazepine use (aIRR 1.75; 95% CI 1.1, 2.78) and homelessness (aIRR 1.35; 95% CI 1.06, 1.73) were predictors associated with an increased number of reported overdose reversals. Mortality was higher among those who reported at least one overdose reversal (HR 3.4; 95% CI 2.2, 5.2).

Conclusions: An NSP's existent framework can be utilised to effectively implement a THN program, provide basic training and reach numerous high-risk individuals. During the four-year study, THN participants reversed a sizeable number of potentially fatal overdoses, of which many were reported by participants whose primary drug was not opioids. Naloxone refill rate was high, indicating that participants were motivated to maintain a supply of naloxone in case of future overdose events.