Buprenorphine deaths confirmed by toxicology reveal a low proportion of opioid agonist treatment before death in Finland.

We studied opioid agonist treatment (OAT) status before buprenorphine-related death in Finland, where buprenorphine is the principal OAT medicine and also the most misused opioid, through a retrospective population-based study using medico-legal cause-of-death investigation and OAT patient records. The study included all death cases (N = 570) between 2018 and 2020 with a buprenorphine or norbuprenorphine finding in post-mortem toxicology and with known drug misuse history or concomitant findings of illicit drugs. Of the deceased, 10% had received OAT in the year before death. Less than 1% of individuals < 25 years had received OAT, whereas the proportion in individuals ≥ 25 years was 13% (p < 0.001). There were significantly more females and more fatal poisonings (p < 0.001) among those < 25 years than among those ≥ 25 years. OAT medication at the time of death was sublingual buprenorphine-naloxone in 74% and subcutaneous buprenorphine in 23%. Except for significantly fewer benzodiazepine findings among those receiving OAT, minimal differences were found in terms of age, gender, cause and manner of death, or concomitant substance use between the deceased in and outside of OAT. Concomitant misuse of benzodiazepines, psychostimulants, alcohol, and gabapentinoids was frequent both in and outside of OAT and likely contributed to the death. These results suggest that access to OAT especially for young people and treatment of multiple addictions should be improved. Comprehensive information from medico-legal cause-of-death investigation as a starting point, combined with subsequent ante-mortem patient records, proved to be a successful approach to shed light on the Finnish scene of buprenorphine mortality.