(7) Xylazine Positivity Rate Among Patients at an Urban Low-Barrier Access Clinic

Background & Introduction
Xylazine, a veterinary sedative, and alpha-2 adrenergic agonist, has increasingly been identified as an adulterant in the opioid drug supply, particularly fentanyl. Its use is associated with sedation and necrotic skin ulcerations, potentially compounding the risks of opioid use disorder.
Limited data are available on the rate of xylazine contamination in the opioid drug supply. The most recent publicly reported data, from March 2022, indicated that 91% of tested samples of purported heroin or fentanyl in Philadelphia (a drug market closely resembling Camden's) contained xylazine. However, human data on xylazine exposure in this community are scarce, apart from its detection in 34% of overdose deaths in 2022.
This study evaluates the prevalence of xylazine exposure by analyzing urine drug screens (UDS) from patients presenting to an urban, low-barrier access, walk-in addiction medicine clinic. Understanding the extent of xylazine exposure in this population can help inform local harm reduction efforts, improve clinical care, and address public health challenges arising from this evolving and dangerous trend in the drug supply.
Methods
This study was conducted at an urban, low-barrier access, walk-in addiction medicine clinic providing harm reduction and clinical services. All patients who underwent UDS as part of routine clinical care between September 19, 2023, and September 19, 2024, were included in the analysis.
Patients who tested positive for fentanyl on UDS were further screened for xylazine using LC/MS-MS, a definitive analytical method. Demographic data, including race and sex, were collected from the electronic medical record.
The prevalence of xylazine positivity was calculated among fentanyl-positive patients. Subgroup analyses were conducted to evaluate potential associations between xylazine exposure and patient characteristics.
This quality assurance project was designed to provide insight into xylazine exposure in an urban clinic setting and to inform harm reduction and clinical care strategies for vulnerable populations.
Results
During the study period, a total of 6,096 urine drug screens (UDS) were performed, of which 2,516 (41.27%) tested positive for fentanyl. Among the fentanyl-positive samples, 2,312 (91.89%) were also positive for xylazine, while 204 (8.11%) tested negative. The average fentanyl concentration across all fentanyl-positive samples was 214.08 ng/mL (SD: 193.37). When stratified by xylazine presence, the average fentanyl concentration was significantly higher in xylazine-positive samples at 220.49 ng/mL (SD: 182.52, range: 1–1863) compared to 140.64 ng/mL (SD: 280.40, range: 1–3038) in xylazine-negative samples (Two Sample t-Test, p < 0.001).
Xylazine positivity was consistently high across all demographic groups. There was no statistical difference in xylazine positivity rates between genders (X2, p=.898). Among fentanyl-positive samples from female patients (n = 787, 31.28% of encounters), 724 (92.00%) tested positive for xylazine, while 63 (8.00%) were negative. Among fentanyl-positive samples from male patient encounters (n = 1,729, 68.72% of encounters), 1,588 (91.84%) were xylazine-positive, and 141 (8.16%) were negative.
Racial distribution showed similarly high rates of xylazine positivity with no statistical differences (X2, p= .416). Among White (non-Hispanic) patient encounters positive for fentanyl (n = 1,430, 56.84%), 1,321 (92.38%) also tested positive for xylazine, while 109 (7.62%) tested negative. African American patient encounters (n = 749, 29.77%) had a xylazine positivity rate of 90.52% (678 positive, 71 negative). Hispanic patient encounters (n = 219, 8.70%) had a xylazine positivity rate of 93.15% (204 positive, 15 negative). Patient encounters categorized as Other (n = 118, 4.69%) had a positivity rate of 92.37% (109 positive, 9 negative).
Conclusion & Discussion
Over 91% of the fentanyl-positive patients presenting to this urban, low-barrier access, addiction medicine walk-in clinic tested positive for xylazine. This finding demonstrates an alarmingly high prevalence of xylazine in the Camden area drug supply. There was no statistical difference in xylazine exposure between gender or racial groups. The significantly higher fentanyl concentrations in xylazine-positive samples may represent a variety of differences among these groups and warrants further investigation.
The data confirms that xylazine has become deeply embedded in the regional drug supply, posing additional risks to people who use opioids. There is an urgent need for expanded harm reduction initiatives, including xylazine test strip distribution, education for both providers and people who use drugs, and the development of treatment protocols addressing xylazine-related complications. Ongoing surveillance of the evolving drug supply remains essential to mitigate emerging threats and improve outcomes for individuals with OUD.