Xylazine detection in urine of fentanyl-positive patients from a single academic center.

Introduction: Xylazine has increasingly been used as an additive in illicit drugs, leading to severe health consequences. The current study aims to define the total xylazine-positive cases since 2010 and to analyze the trends and clinical implications of xylazine-positive cases at the University of Pittsburgh Medical Center from 2020 to 2024.

Methods: This cross-sectional academic laboratory-based study analyzed the mass spectrometry dataset, including the normalized peak sizes of xylazine and fentanyl in xylazine-positive urine comprehensive drug screening cases, along with their clinical information. The laboratory information system was also queried to obtain the total number of xylazine detections in urine comprehensive drug screening since 2010.

Results: A total of 351 xylazine-positive adult cases in urine comprehensive drug screening were examined to identify trends in urine xylazine and fentanyl relative concentrations between 1 April 2020 and 31 March 2024. After excluding outpatient cases, the urine xylazine and fentanyl relative concentrations were also correlated with clinical features for the remaining 249 cases. Xylazine-positive cases have increased since 2016, with a sharp rise between 2019 and 2021. Urine xylazine relative concentrations showed a minimal decline, while urine fentanyl relative concentrations modestly decreased. Patients with skin wounds and infections, but not with coma or post-cardiac arrest, had significantly higher urine xylazine relative concentrations than the entire cohort.

Discussion: The number of xylazine-positive and fentanyl-positive cases has increased over time, even as the relative concentrations of urine xylazine and fentanyl have gradually declined. This inverse trend suggests an increasing prevalence of xylazine and fentanyl exposure at progressively lower concentrations. Our data also indicated the association of urine xylazine concentrations with skin wounds and infections, but not with coma or post-cardiac arrest.

Conclusions: The findings of this study highlight the increasing prevalence of xylazine in illicit drug use, particularly in combination with fentanyl, at our institution over time. More research is needed to elucidate the roles of xylazine on opioid intoxication.