Prevalence of p-Fluorofentanyl and Xylazine in Postmortem Fentanyl Casework

In the United States (U.S.), fentanyl remains the leading drug associated with opioid-related deaths. Many analogs of fentanyl have been identified and linked to the opioid overdose epidemic. After core-structure scheduling of illicitly manufactured fentanyl (IMF) and related products, para-fluorofentanyl (p-FF) reemerged with varied prevalence in the U.S. Xylazine also emerged as a cutting agent in IMF. The aim of this study was to describe the prevalence and trend use patterns of fentanyl, p-FF, and xylazine in a case series from 2021 to 2023 in the state of Florida. A three-year retrospective analysis of data was conducted. A total of 8121 cases were submitted for analysis over the period of study. Among them, 1530 cases (18.8%) tested positive for fentanyl in one or more of the specimens submitted for these cases. The age of the decedents ranged 16–85 years, with the majority being White males. The concentration range of fentanyl in the blood specimens (n = 1358) analyzed was 2.5–579 ng/mL. p-FF was detected with fentanyl in 164 postmortem blood specimens with a concentration range of 2.5–65 ng/mL. Xylazine was identified in the urine of 391 decedents. The combination of fentanyl, p-FF, and xylazine was detected in 70 cases. When fentanyl co-occurred with both xylazine and p-FF, it was primarily observed with benzodiazepines, cocaine, methamphetamine, and other opioids. This study aimed to provide a better understanding of the fentanyl analog and adulterant prevalence in Florida.