B-311 Increasing Xylazine Findings in Clinical Samples

Abstract

Abstract Background Xylazine is a veterinary tranquilizer first appearing in illicit fentanyl preparations in 2019. It is believed to extend a fentanyl high and is now more commonly used as its own drug of abuse. Clinically, xylazine is of concern as it does not respond to naloxone or other antidote during overdoses. There are many forensic findings of increasing xylazine use since its original appearance, but little in the literature concerning clinical xylazine findings, possibly because xylazine is rarely screened in routine drug screening. We sought to find clinical cases with positive xylazine results from 2019–2022. Determined data included demographics (where possible to discern), sex distribution, age ranges, and frequency. Methods We queried our laboratory information management system (LIMS) for reported xylazine findings under expanded clinical drug screen utilizing liquid chromatography time of flight mass spectrometry (LC-TOF) for screening and liquid chromatography tandem mass spectrometry (LC-MS/MS) for confirmation, and specific xylazine testing utilizing LC-MS/MS. Results In 1928 clinical cases reported between January 2019 and January 2023, the xylazine positivity rate increased from 1.28% (2021; n = 13 positive xylazine results) to 5.05% positivity (2022; n = 29 positive xylazine results) despite a significant decrease in panels and tests with xylazine ordered (n = 1008 in 2021, n = 574 in 2022). The ages of the patients ranged 0–57 years; eleven cases concerned pediatric patients. Of cases that indicated the sex of the patient, 69% were male (n = 29). These cases were found in ten different states (AZ, CT, DE, IN, MA, NJ, OH, PA, UT, VA), with 18 incidental findings. While other drugs were present in incidental finding cases, all cases with an incidental positive xylazine result were also positive for fentanyl and norfentanyl, and several cases were also positive for fentanyl analogues, most commonly 4-ANPP, which occurred in 50% of these cases. Conclusion Xylazine use continues to be on the rise and should be of concern for emergency medicine doctors, poison control centers, and clinical laboratories.