UMEM Educational Pearls

Category: Toxicology

Title: Xylazine in heroin/fentanyl

Keywords: xylazine, adulterate, heroin, fentanyl (PubMed Search)

Posted: 12/16/2021 by Hong Kim, MD (Emailed: 12/23/2021)
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Xylazine is a central alpha-2 agonist (similar to clonidine) that is used as a veterinary tranquilizer. It also possesses analgesic, and muscle relaxant properties. Heroin/fentanyl is increasingly being adulterated with xylazine and resulting in severe adverse effects (CNS and respiratory depression, bradycardia, and hypotension), including deaths. 

According to CDC, 0.1%-5.5% of IMF death in US between 2019 – 2020 involved xylazine. 

In Philadelphia, PA:

The detection of xylazine in unintentional overdose death increased from

  • 2010 – 2015: 2%
  • 2016: 11%
  • 2017: 10%
  • 2018: 18%
  • 2019: 31%

Approximately 25% of drug seizures in Philadelphia contained xylazine in 2019


There is no effective pharmacologic agent for xylazine toxicity. Similar to clonidine toxicity, high dose naloxone may be tried. But pediatric data show that approximately 50% of pediatric clonidine toxicity response to high-dose naloxone administration. Thus, naloxone administration may not reverse the CNS/respiratory depression, bradycardia and hypotension.



  • There is increasing adulteration of heroin/fentanyl with xylazine
  • Naloxone administration may not reverse the toxicity of xylazine


O’Donnell J, Tanz LJ, Gladden RM, Davis NL, Bitting J. Trends in and Characteristics of Drug Overdose Deaths Involving Illicitly Manufactured Fentanyls — United States, 2019–2020. MMWR Morb Mortal Wkly Rep 2021;70:1740-1746. DOI: icon.

Johnson J, et alInj Prev 2021;27:395–398. doi:10.1136/injuryprev-2020-043968