Xylazine-Involved and Xylazine-Associated Deaths in Cook County, IL

"A xylazine-associated death was defined as a positive postmortem xylazine serum toxicology test result in an unintentional, undetermined, or pending intent substance-related death during January 2017–October 2021. Routine postmortem tests were conducted for other substances including fentanyl, fentanyl analogs, cocaine, and naloxone. Xylazine testing is standard in Cook County for suspected drug overdose deaths. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.*

"A total of 236 xylazine-associated deaths were reported during the study period. Xylazine-associated deaths increased throughout the study period; incidence peaked during July 2021 (Figure). The percentage of fentanyl-associated deaths involving xylazine also increased throughout the study period, rising to a peak of 11.4% of fentanyl-related deaths assessed by the Cook County Medical Examiner’s Office during October 2021. Fentanyl or fentanyl analogs were detected on forensic testing in most xylazine-involved deaths (99.2%). Other common co-occurring substances included diphenhydramine (79.7%), cocaine (41.1%), and quinine (37.3%). Naloxone was detected in 32.2% of xylazine-associated deaths."