Drug traffickers now use the sedative xylazine as an adulterant for other illicit drugs and mix it to enhance or alter the effect. People who use drugs such as heroin, fentanyl or cocaine adulterated with xylazine increase their risk of fatal overdose, often unaware that they are taking the sedative. One of the big risks of xylazine overdose is that people may not even realize they`re taking it. One study showed that 22% of street drug users who tested positive for xylazine did not know they had taken it. This is likely due to the fact that xylazine is often added to illicit drugs such as cocaine, heroin and fentanyl to enhance or influence their effects. Xylazine is a sedative used in animals that can be used as a muscle relaxant and analgesic. Although the drug is sometimes known as a sedative for horses, xylazine is used to treat a variety of animals, including cats, dogs, cattle, sheep, horses, deer, moose, and even rats. The drug xylazine has made headlines for its role in increasing overdose deaths. In 2019, the Centers for Disease Control and Prevention found xylazine in 5.8 percent of overdose deaths. In the first six months of 2020, that figure nearly doubled to 11.4 percent. In 1979, the first case of xylazine toxicity was reported in a 34-year-old man who had treated himself for insomnia with an injection of 1 g of xylazine.  Deliberate poisoning by ingestion, inhalation or injection of xylazine has been reported.
Intravenous use is the most common route of administration for people who abuse heroin or xylazine recreationally. In Puerto Rico, xylazine has grown in popularity. Its use was associated with a high number of inmate deaths at Guerrero Correctional Facility in Aguadilla, Puerto Rico, from 2002 to 2008. In veterinary anesthesia, xylazine is often used in combination with ketamine. It is sold worldwide under many brand names, including Bayer`s Rompun brand.  It is also marketed under the names Anased, Sedazine and Chanazine.  Interactions with different animals vary.    Number and percentage of accidental overdose deaths of heroin and/or fentanyl with xylazine, Philadelphia, Pennsylvania, 2010-2019. The results of this study suggest that the opioid epidemic continues to evolve in the United States.
Although xylazine has been a drug used in Puerto Rico since the early 2000s, deadly toxicological data on overdoses from Philadelphia and other countries suggest that its prevalence may increase in the continental United States.5 6 Jurisdictions that do not currently test xylazine should consider including it in their routine toxicology tests. Further studies are needed to understand the synergistic effects of human use of fentanyl and xylazine and to better contextualize the reasons for its use in the United States. Xylazine is a pharmaceutical drug used for sedation, anesthesia, muscle relaxation and analgesia in animals such as horses, cattle and other non-human mammals.  Veterinarians also use xylazine as an emetic, especially in cats.  It is a clonidine analogue and an α2 agonist of the adrenergic receptor.  There are limited data on xylazine withdrawal. Unfortunately, fatal xylazine overdoses are common, so there were few ways to study the withdrawal symptoms of a person who used xylazine long-term. Some experts theorize that the drug may have withdrawal symptoms similar to other tranquilizers such as benzodiazepines. It can be difficult to know if a person is using xylazine because the side effects are similar to other central nervous system sedatives. Common side effects of xylazine in humans include: Xylazine is a non-opioid sedative, analgesic, and muscle relaxant used in veterinary medicine.1 Human use of xylazine in people who use drugs has been well documented in Puerto Rico since the early 2000s, where it is known as “Anestesia de Caballo” (equine anesthesia).2–4 More and more cases of xylazine in the supply of illicit drugs in mainland China and the United States, although the reasons for its inclusion in the drug supply are unclear.5 6 In the United States, xylazine is not a planned drug, and although it is approved for use in veterinary medicine, the Food and Drug Administration has not approved it for human use. In humans, xylazine can cause hypotension, central nervous system depression, respiratory depression and bradycardia.1 In addition, associations have been made between xylazine use and open skin ulcers in people who inject xylazine.2 4 Research is limited to the effects of xylazine in combination with opioids and information about its presence in the continental United States.
Especially in fentanyl-dominated markets. In Philadelphia, xylazine`s street name is “tranq,” and heroin and fentanyl cut with xylazine are called “tranq dope.” This study examines trends in the detection of xylazine in postmortem toxicology testing in overdose deaths in Philadelphia, Pennsylvania, a city where fentanyl has largely replaced heroin in the illicit drug market since 2015.