TOPLINE: 

Patients with opioid overdose who tested positive for xylazine in the emergency department (ED) had higher rates of bradycardia (6.3% vs 2.6%) than those who tested negative and were mostly from the Northeast region of the US, according to a new study.

METHODOLOGY:

• Researchers conducted the Toxicology Investigators Consortium (ToxIC) Fentalog Study, a multicenter, prospective observational cohort study involving 18 EDs across 10 healthcare institutions in the US from 2020 to 2023.
• The analysis included 1289 patients who presented with suspected opioid overdose, received naloxone, or reported opioid use and had waste blood available for toxicologic testing.
• The primary outcome was the detection of xylazine in patient serum using liquid chromatography with quadrupole time-of-flight mass spectrometry.
• Other outcomes included the clinical and demographic variables associated with xylazine among patients presenting to the ED with opioid overdose.

TAKEAWAY:

• Xylazine was detected in 22.6% of patients, who were older (mean age, 44.8 years), primarily men (78%), White individuals (48%), non-Hispanic individuals (82%), and mostly from the Northeast region in the US (74.9%).
• Patients testing positive for xylazine had higher co‑detection of benzodiazepines (37.0% vs 28.4%; P = .005), had higher rates of bradycardia on initial ED vital signs (6.3% vs 2.6%; P = .005), received lower median total naloxone doses (3.75 mg vs 6.88 mg), experienced fewer ICU admissions (10.9% vs 17.4%; P = .02), and had fewer cardiopulmonary resuscitation events (4.6% vs 12.8%; P = .01) than those testing negative for xylazine.
• Factors associated with higher odds of xylazine detection were bradycardia on initial ED vital signs (adjusted odds ratio [aOR], 2.26) and an age of 60 years or above (aOR, 2.33).
• Factors associated with lower odds of xylazine detection included Hispanic ethnicity (aOR, 0.62) and tachycardia on initial ED vital signs (aOR, 0.62).

IN PRACTICE:

"We found that bradycardia on initial vital signs was associated with an increased likelihood of xylazine detection on serum testing. These novel findings help in starting to characterize the clinical toxicity associated with xylazine-adulterated fentanyl," the authors wrote.

SOURCE:

The study was led by Jennifer S. Love, Icahn School of Medicine, Mount Sinai, New York City. It was published online on January 13, 2026, in Addiction.

LIMITATIONS: 

Waste clinical specimens were unavailable for approximately one quarter of screened patients. Blood testing allowed only qualitative detection of substances, precluding assessment of exposure levels or quantitative analysis. The timing and detection window of xylazine use were unknown, and substances detected on serum sampling may have reflected prior exposure rather than the nonfatal overdose associated with the ED visit. Additionally, the study included only ED-treated overdoses at urban US sites, limiting the generalizability of the findings.

DISCLOSURES:

The study was funded by the National Institute on Drug Abuse of the National Institutes of Health and the Centers for Disease Control and Prevention. The authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.