Xylazine is sold under the names Rompun, AnaSed, Sedazine, and Chanazine. It is a nonopioid alpha-2 adrenergic agonist veterinary anesthetic agent that inhibits the release of norepinephrine and dopamine in the central nervous system, resulting in the clinical effects of sedation and analgesia. The US Food and Drug Administration (FDA) does not approve it for human use. However, it has been identified as a drug of abuse and an adulterant in street drugs.

Xylazine has recently emerged as a drug of concern in the United States, as its prevalence as a drug of abuse and as an adulterant in street drugs has significantly increased. Its presence in overdose deaths in the United States has increased from 0.36% of deaths in 2015 to 6.7% in 2020. Xylazine alone can be ingested, smoked, snorted, or injected, producing various effects, depending on the dose administered. It can produce energizing effects and hypertension at a minute dose, but increasing doses cause sedative effects, bradycardia, and hypotension that can progress to hemodynamic instability and respiratory arrest. See alpha-2 adrenocepter agonist poisoning for treating xylazine overdose.

Xylazine is an increasingly common additive to street drugs such as fentanyl, heroin, and cocaine. It is thought to serve as a bulking agent to increase the supply of drug products and reportedly extends the duration of the opioid effect when combined with fentanyl and heroin. Xylazine has been detected across the United States, but Pennsylvania, Maryland, and Connecticut have the highest reported prevalence.

Chronic injection use of xylazine, either intentionally or unintentionally with adulterated drugs, has been associated with the development of abscesses and ulceration that primarily occur on the extremities. Skin ulceration is thought to occur due to direct vasoconstriction of vessels supplying the skin. The decreased perfusion of soft tissues subsequently impairs wound healing and increases the risk of infection, ulceration, and skin necrosis. Ulcerations may occur more diffusely, not limited to the drug injection site.

Without treatment, these lesions can progress to cause osteomyelitis, bacteremia, sepsis, and, in serious cases, amputation of extremities and severe disability.