Notes from the Field: Xylazine, a Veterinary Tranquilizer, Identified as an Emerging Novel Substance in Drug Overdose Deaths — Connecticut, 2019–2020

Xylazine, a clonidine analog, is a nonopioid veterinary tranquilizer not intended for human use. Recreational drugs such as cocaine, heroin, and fentanyl are often adulterated with agents such as xylazine to enhance drug effects or increase street value by increasing net weight (1). Xylazine is known to cause hypotension and bradycardia when used in humans (2). Although not a controlled substance in the United States, xylazine cannot be purchased without a veterinary license. Misuse of xylazine was reported in Puerto Rico in the early 2000s (3). Recreational use of xylazine can occur via oral ingestion, inhalation or sniffing, or intravenous injection; however, injection is the most common route of administration (2). The effects of xylazine when used contemporaneously with other illicit drugs such as heroin, cocaine, and fentanyl are still not widely known (2). No antidote is recommended for the effects of xylazine overdose (4). One recent study suggests that high doses of naloxone might reverse the effects of a clonidine overdose (5). However, given that this finding is from a single study of a small cohort of pediatric patients, it might not be generalizable to the broader population (5). Furthermore, no reports specific to xylazine and naloxone exist regarding reversal of effects.