Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Jul 22:16:100364.
doi: 10.1016/j.dadr.2025.100364. eCollection 2025 Sep.

Xylazine prevalence and concentration in the Los Angeles fentanyl market, 2023-2025

Joseph Friedman  1 , Caitlin A Molina  2 , Adam J Koncsol  2 , Ruby Romero  2 , Morgan E Godvin  2 , Elham Jalayer  3 , Spider Davila  4 , Oscar Arellano  5 , Amanda Cowan  4 , Brian Hurley  6 , Chelsea L Shover  2
Affiliations

Xylazine prevalence and concentration in the Los Angeles fentanyl market, 2023-2025

Joseph Friedman et al. Drug Alcohol Depend Rep. .

Abstract

Background: The veterinary sedative xylazine has been mostly described on the East Coast-yet early reports indicate that it is now arriving to West Coast fentanyl markets. Emerging drug checking approaches can provide information about the concentration and prevalence of xylazine in illicit fentanyl.

Methods: Fentanyl samples from a community-based drug checking program in Los Angeles, California were assessed using direct analysis in real time mass spectrometry (DART-MS). A subset was analyzed with liquid chromatography-mass spectrometry (LC-MS) to quantify the concentration of xylazine, fentanyl, and other compounds.

Results: Among n = 536 fentanyl-positive samples, n = 103 were xylazine-positive, and n = 78 had quantitative results available. Xylazine positivity rose from 0 % in 2023 quarter 1 to a peak of 29.5 % in 2025 quarter 1. A significant time trend was observed (OR per quarter year= 1.35 [95 %CI: 1.19-1.52]). Xylazine concentration in fentanyl samples was generally low, with a highly skewed distribution (mean=2.42 %, sd=7.80 %). 76.9 % of xylazine-positive samples had <1.0 % xylazine concentration. Compared to xylazine-negative samples, xylazine-positive samples were more likely to contain bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (BTMPS) [46.60 % vs 17.30 %], and lidocaine (65.0 % vs 29.6 %), and had lower average fentanyl concentration (6.12 % vs 10.7 %).

Conclusions: We note increasing xylazine positivity among samples of illicit fentanyl in Los Angeles, California. The distribution of xylazine concentration is highly skewed, with a small number of very high concentration samples, and majority with <1 %. Nevertheless, more research is needed to study the health impacts of even the low concentration xylazine that is most predominant here; the average participant may still be exposed to a physiologically significant dose of xylazine.

Keywords: Epidemiology; Overdose crisis; Quantitative; Trend analysis; West Coast; Xylazine.

PubMed Disclaimer

Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Xylazine positivity among fentanyl-positive samples, 2023Q1–2025Q2. Xylazine positivity among fentanyl-positive samples brought to drug checking services in Los Angeles are shown by quarter, between the first quarter (Q1) of 2023 and the second quarter (Q2) of 2025.
See this image and copyright information in PMC

Update of

Similar articles

See all similar articles

Cited by

References

    1. Anaesthesia of the Dog . Veterinary Anaesthesia. Elsevier; 2014. pp. 405–498. - DOI
    1. Appley M.G., Robinson E.L., Thomson A., Russell E., Sisco E. An analytical platform for near real-time drug landscape monitoring using paraphernalia residues. Forensic Chem. 2023;34 doi: 10.1016/j.forc.2023.100489. - DOI
    1. Bowles J.M., McDonald K., Maghsoudi N., Thompson H., Stefan C., Beriault D.R., Delaney S., Wong E., Werb D. Xylazine detected in unregulated opioids and drug administration equipment in Toronto, Canada: clinical and social implications. Harm Reduct. J. 2021;18:104. doi: 10.1186/s12954-021-00546-9. - DOI - PMC - PubMed
    1. Bufanda L.P., Montoya A.G., Carrillo B.T., Tejeda M.A.G., Segovia L.A., Calderón-Villarreal A., Friedman J.R. Managing xylazine-involved overdoses in a community harm reduction setting: lessons from Tijuana, Mexico. Harm Reduct. J. 2025;22:2. doi: 10.1186/s12954-024-01143-2. - DOI - PMC - PubMed
    1. Cano M., Daniulaityte R., Marsiglia F. Xylazine in Overdose Deaths and Forensic Drug Reports in US States, 2019-2022. JAMA Netw. Open. 2024;7 doi: 10.1001/jamanetworkopen.2023.50630. - DOI - PMC - PubMed

LinkOut - more resources