Xylazine Toxicity

Xylazine is a non-narcotic compound utilized for sedation, pain relief, and muscle relaxation in veterinary medicine, where it is often referred to as "anestesia de caballo" or "horse anesthetic." Also known as N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiazin-2-amine, xylazine is a clonidine analog discovered by Farbenfabriken Bayer in 1962 in Germany promoted for use as an antihypertensive. Approval was not granted for human use as an antihypertensive due to profound hypotension and excessive central nervous system depression. Xylazine was later introduced as a sedative, emetic, analgesic, and muscle relaxant for veterinary use. The use of xylazine in animals was first reported in the late 1960s, and it is currently approved for use as a nonopioid tranquilizer in veterinary medicine. Xylazine is frequently used with ketamine as an anesthetic agent for experimental studies involving dogs, cats, horses, rabbits, and rats.

Xylazine emerged as a popular illegal substance among those who inject drugs in Puerto Rico in the early 2000s. Currently, there is limited information about the unlawful consumption, geographic prevalence, and immediate or long-term effects of xylazine on humans. Recently, xylazine misuse has surged in the northeastern United States, spreading across many states, as evidenced by the rising number of samples testing positive for the drug.

In Philadelphia, xylazine is popularly referred to as "tranq"; when xylazine is mixed with more prevalent illegal opioids like heroin or fentanyl, the mixture is called "tranq dope." Xylazine is frequently combined with synthetic opioids, primarily fentanyl, in the unregulated market. Additionally, xylazine has been found alongside cocaine and methamphetamine and, more recently, mixed with oxycodone and alprazolam. Xylazine was reportedly diverted from the veterinary market to the recreational drug market in Puerto Rico.

Xylazine has spread rapidly due to several factors, including cost-cutting, an increase in its addictive properties, and its ability to extend the duration of the opioid with which it is combined. Xylazine poses a challenge to the United States healthcare system and those who use it knowingly or unknowingly due to its benefits to the illegal drug industry, a lack of information, and the absence of an approved antidote.