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.