Xylazine is a sedative approved by the FDA exclusively for veterinary use. It produces sedation, pain relief, and muscle relaxation in animals, primarily horses and cattle. In recent years, it has gained widespread attention because it is increasingly found mixed into the illicit drug supply, particularly with fentanyl, where it poses serious and sometimes fatal risks to humans.
How Xylazine Works in Animals
Xylazine works by activating receptors in the central nervous system that reduce the release of two key signaling chemicals: norepinephrine (which drives alertness and arousal) and dopamine (which plays a role in movement and motivation). The result is a calm, sedated animal with relaxed muscles and reduced pain sensitivity.
Veterinarians most commonly use xylazine for procedures that require an animal to stay still, such as dental work, wound treatment, minor surgeries, and diagnostic imaging. In horses, typical intravenous doses range from 0.2 to 1.0 mg/kg of body weight, adjusted depending on the level of sedation needed. It’s also used in cattle and other large animals, sometimes in combination with other sedatives or anesthetics to deepen the effect. Importantly, xylazine has a veterinary reversal agent that can quickly wake the animal if needed.
Why Xylazine Is Showing Up in Street Drugs
Xylazine has become a common additive in illicit fentanyl and other street drugs, earning the nickname “tranq” or “tranq dope.” DEA laboratory analysis shows that xylazine is most frequently found in polydrug mixtures, often alongside fentanyl. The combination is believed to extend the duration of the high, which makes it attractive to both suppliers and some users.
The spread of xylazine in the drug supply has followed a pattern similar to fentanyl itself. It first appeared heavily in white powder heroin markets in the Northeast, which still reports the highest overall numbers. From there it moved south, with southern states reporting a 193 percent increase in xylazine cases over a recent two-year period. The West saw a nearly 112 percent increase over the same timeframe. Xylazine is now present in drug markets across the country.
Despite its growing role in overdose deaths, xylazine is not a controlled substance under federal law. It remains legal to purchase through veterinary supply channels, which contributes to its availability.
What Xylazine Does to the Human Body
Xylazine was never intended for human use, and it affects the body in ways that are both dangerous and difficult to treat. According to the FDA, signs of acute xylazine toxicity include slowed breathing, dangerously low blood pressure, a slow heart rate, abnormally low body temperature, constricted pupils, and elevated blood sugar. The combination of low blood pressure and a slow heart rate is a particularly telling sign that xylazine may be involved in an overdose.
In humans who tested positive for both fentanyl and xylazine, the median half-life of xylazine was about 12 hours, with a range of roughly 6 to 21 hours. That means the drug’s sedating and breathing-suppressing effects can linger long after other substances have worn off, creating an extended window of danger.
Skin Wounds Linked to Xylazine Use
One of the most alarming consequences of xylazine exposure is severe, necrotic skin wounds. These are not ordinary injection-site infections. At injection sites, they typically start as small abscesses with blisters, then progress into larger purple, oxygen-starved areas. At sites distant from where the drug was injected, deep oblong wounds with areas of dead tissue can develop. In the worst cases, these wounds expose tendons and bone. The bone itself can become so infected with osteomyelitis that it crumbles spontaneously, sometimes leading to amputation.
The wounds likely develop through two overlapping mechanisms. First, xylazine appears to cause direct tissue toxicity, almost like a chemical burn. Second, it constricts local blood vessels, cutting off blood flow and oxygen to surrounding tissue. With repeated injections, the damage compounds. Surgeons have noted that milder cases involve patches of reddened and blackened skin, while severe presentations can mimic necrotizing fasciitis, a life-threatening flesh-eating infection. One key difference: patients with xylazine wounds usually have normal vital signs, low-grade or no fever, and normal blood counts, while true necrotizing infections cause extreme pain, high fever, rapid heart rate, and sepsis.
Why Naloxone Alone Is Not Enough
Naloxone, the overdose-reversal medication carried by first responders and available over the counter, does not reverse the effects of xylazine. This is a critical distinction. Naloxone works specifically on opioid receptors, and xylazine is not an opioid. Because xylazine is almost always mixed with fentanyl or other opioids, naloxone should still be administered during a suspected overdose. It will counteract the opioid component. But the breathing suppression and sedation caused by xylazine will continue even after naloxone takes effect.
The CDC recommends that anyone responding to a potential xylazine-involved overdose give naloxone, call 911, and provide rescue breaths. First responders have reported that rescue breathing is especially helpful in these situations because xylazine’s primary danger is how profoundly it slows respiration. If naloxone doesn’t fully revive someone, xylazine should be considered as a contributing factor. Staying with the person until emergency medical help arrives is essential, since the drug’s effects can outlast the window of naloxone’s action.