The Prevalence of Xylazine in Patient Urine Samples That Were Positive for Fentanyl in Western New York

Xylazine, a veterinary sedative, is increasingly being discovered in the illegal drug supply across the United States and is associated with overdose fatalities. Not approved for human use, xylazine poses life-threatening risks, particularly when used in conjunction with opioids such as fentanyl. This study evaluates the prevalence of xylazine in urine samples that screened positive for fentanyl. The evaluation involved measuring the parent drug xylazine and its metabolites, xylazine glucuronide and hydroxy-xylazine, as well as finding their correlation with fentanyl and norfentanyl concentrations in patient samples.

Samples were collected over a one-month period. Urine samples were analyzed for fentanyl, norfentanyl, and 3 xylazine-specific analytes (i.e., xylazine, xylazine glucuronide, and hydroxy-xylazine). Briefly, reverse-phase chromatographic separation was performed on a Bonshell Phenyl-Hexyl column utilizing a binary mobile phase gradient. The eluents were detected through positive electrospray ionization and multiple reaction monitoring analysis on a triple quadrupole mass spectrometer.

Out of a total of 230 urine samples, 184 were confirmed positive for fentanyl. Xylazine was detected in 56 out of the 184 fentanyl-positive samples, accounting for 30% of the fentanyl-positive confirmatory test. Xylazine (or its metabolites) was not observed in fentanyl-negative samples. Furthermore, the parent xylazine drug was detected in all 56 samples, whereas the metabolite glucuronide and hydroxy forms were only detected in 28 and 6 samples, respectively.

This study estimated a xylazine prevalence of 30% in fentanyl-positive urine samples within our local Western New York population. This study represents the first report within our clinical population.