Buprenorphine involvement in opioid overdose deaths: A retrospective analysis of postmortem toxicology in Marion County, Indiana, 2015-2021.

Background: Amidst an unprecedented overdose epidemic, the opioid partial agonist buprenorphine is a medication for opioid use disorder associated with reductions in overdose. Despite its efficacy, buprenorphine prescribing remains closely regulated, owing to concerns about misuse, and its possible role in overdoses. Methods: A retrospective analysis of the Marion County, Indiana coroner's postmortem toxicology data for unintentional opioid-involved overdose deaths from 2015 through 2021. The county was chosen as a novel setting whose corner provided comprehensive overdose data. It contains Indianapolis, a large city in the US Midwest The 2,369 opioid-involved overdoses were analyzed for the presence of buprenorphine and its metabolite, as wel as potent substances associated with illicit drug use and overdose. Results: Of the 2,369 postmortem toxicology records analyzed, 55 (2.3%) indicated presence of buprenorphine. Of buprenorphine-involved cases, 51 (92.7%) involved other potent substances such as fentanyl, heroin, cocaine, methadone, and amphetamines; 4 (7.3%) were attributed to buprenorphine and liver failure, diabetic ketoacidosis, or relatively less potent substances. Fentanyl was present in 28 cases (50.9%), benzodiazepines were present in 24 (43.6%). Black opioid decedents were considerably less likely to have buprenorphine in their toxicology than White decedents. Conclusions: Buprenorphine was rarely detected in the postmortem toxicology of unintentional opioid overdoses in a major US city in the Midwest. In nearly all cases it was accompanied by other potent substances that more frequently cause fatal overdoses on their own. This study confirms findings from other geographic settings that the overdose mortality risks associated with buprenorphine are low.