Xylazine is a powerful sedative approved for use in animals, not humans. It works by triggering receptors in the central nervous system that reduce the release of key signaling chemicals, producing deep sedation, pain relief, and muscle relaxation. Originally developed for veterinary medicine, xylazine has increasingly appeared in the illicit drug supply, where it poses serious and distinct risks to people who encounter it.
How Xylazine Works in the Body
Xylazine activates a type of receptor in the brain and spinal cord called the alpha-2 adrenergic receptor. When these receptors are switched on, they dial down the release of norepinephrine and dopamine, two chemicals that keep you alert, regulate your heart rate, and maintain blood pressure. The result is heavy sedation, pain relief, and relaxed muscles. The drug may also interact with several other receptor systems in the brain, which helps explain its broad range of effects.
Because xylazine acts on the nervous system rather than on opioid receptors, its sedation is chemically different from what drugs like fentanyl or heroin produce. This distinction matters in an emergency, as explained below.
Its Intended Use: Veterinary Medicine
The FDA has approved xylazine only for use in animals. Veterinarians rely on it primarily for horses, cattle, and deer. A small dose calms a frightened, aggressive, or injured animal enough for a vet to safely examine it in close quarters and treat injuries. In that setting, the drug is carefully dosed by weight and species, and its effects are well understood. It has no approved medical use in people.
Why It’s Showing Up in Street Drugs
Xylazine has become a common adulterant in the illicit fentanyl supply. The combination is sometimes called “tranq” or “tranq dope.” People who use this mixture report that the relaxing and euphoric effects of fentanyl feel amplified and longer-lasting when xylazine is present. For dealers, the drug is cheap and easy to obtain, stretching the supply. For users, the extended sedation can feel desirable but comes with dramatically increased danger.
CDC data shows how quickly xylazine has spread. Among 20 states and Washington, D.C., the percentage of fentanyl-involved overdose deaths that also contained xylazine rose from 3% in January 2019 to 11% by June 2022. Those numbers likely undercount the problem, since many routine toxicology screens don’t test for xylazine at all.
Effects on Humans
When a person is exposed to xylazine, the signs can include severe drowsiness, slowed breathing, dangerously low blood pressure, a slow heart rate, low body temperature, constricted pupils, and elevated blood sugar. The combination of low blood pressure and a slow heart rate together is a hallmark pattern that clinicians associate with xylazine exposure. Breathing can slow to a life-threatening degree, especially when xylazine is combined with opioids like fentanyl, which independently suppress respiration.
One of the most alarming effects is what xylazine does to the skin. The drug’s activation of alpha-2 receptors causes intense constriction of blood vessels. When blood flow to soft tissue is severely restricted, the tissue begins to die. This leads to deep, necrotic ulcers that can be extremely difficult to heal. These wounds don’t only form at injection sites. They can appear on distant parts of the body, including the arms and legs, which increases the risk of serious soft tissue infections, chronic open wounds, and in severe cases, amputation.
Why Naloxone Alone Isn’t Enough
Naloxone (the drug in Narcan) reverses opioid overdoses by blocking opioid receptors in the brain. Xylazine does not act on opioid receptors, so naloxone cannot reverse its effects. If someone has overdosed on a fentanyl-xylazine combination, naloxone will still counteract the fentanyl portion and can restore breathing enough to save a life. It should always be administered when an opioid overdose is suspected. But the person may remain deeply sedated, with low blood pressure and a slow heart rate, because the xylazine component is still active. That means calling emergency services is critical even after naloxone is given.
Withdrawal Symptoms
Xylazine withdrawal is not yet fully characterized, but the symptoms that have been documented include anxiety, irritability, restlessness, and potentially severe spikes in blood pressure. Because most people using xylazine are also dependent on opioids, withdrawal from both substances can overlap and intensify each other. The discomfort of simultaneous withdrawal is significant enough that many people leave treatment early, which is one reason managing both dependencies together is considered essential.
Detecting Xylazine Before Use
Xylazine test strips are now available and have proven highly accurate. A study from the National Institute of Standards and Technology found that these lateral flow test strips detected xylazine at concentrations above 2.5 micrograms per milliliter with a sensitivity of 97.4% and an overall accuracy of 98.6%. In practical terms, if xylazine is present in a drug sample at meaningful levels, the strips will almost certainly catch it. They work similarly to fentanyl test strips: you dissolve a small amount of a substance in water and dip the strip. A single line means xylazine was detected; two lines mean the test is negative.
These strips are increasingly available through harm reduction organizations and some pharmacies, though access varies by state and local law.