Xylazine

Xylazine is a tranquilizer, pain reliever, and central nervous system depressant that is U.S. Food and Drug Administration (FDA)-approved for use in veterinary medicine. It has not been approved for human use. Illicit xylazine is often mixed in with illicit opioids, most frequently fentanyl, but it is not an opioid. Xylazine is also known as “tranq” or, when combined with fentanyl or other opioids, “tranq dope.” Xylazine can be used by injecting, snorting, swallowing, or inhaling.

Xylazine can make people drowsy and cause breathing, heart rate, and blood pressure to slow to dangerously low levels. When people take xylazine with fentanyl, it is not clear if xylazine increases the risk of fatal overdose. However, extreme sedation from xylazine can cause people to stop breathing. Most overdose deaths linked to both xylazine and fentanyl also involved other substances, including cocaine, heroin, benzodiazepines, alcohol, gabapentin, and prescription opioid medications.¹

While opioid overdose reversal medications (such as naloxone and nalmefene) do not reverse the effects of xylazine, public health experts recommend people give overdose reversal medications for overdose with suspected xylazine exposure, because most people are exposed to xylazine by taking fentanyl. 

Xylazine has typically been found in combination with other drugs, especially opioids, such as illicitly manufactured fentanyl. Research suggests that some people use it intentionally to lengthen fentanyl’s euphoric effects.²  However, people who use drugs also report using it by accident, with some telling researchers that it was an unwanted additive to their drugs.^3,4

Because the drug supply evolves quickly, NIDA supports the National Drug Early Warning System (NDEWS), which tracks where substances, including xylazine, appear across the country. 

Xylazine is a central nervous system depressant. This means that it makes people drowsy, slows brain activity, relaxes muscles, and slows heart rate and breathing. At certain doses, xylazine’s effects can be life threatening, especially if it is used with other depressants such as opioids (including fentanyl), alcohol, and benzodiazepines.

People who have used xylazine also report other effects. Repeated xylazine use can cause painful and difficult-to-treat skin and muscle (“soft tissue”) sores. If left untreated, the sores can grow and become infected and lead to patches of dead and dying tissue. In rare severe cases, these may require the affected body part to be amputated. People with these wounds may require ongoing wound management and pain treatment.^5,6,7 The sores can appear at the site of injection. But they often appear elsewhere on the body, and some clinicians report that these wounds happen even when people smoke or snort xylazine but do not inject it.¹⁴  

Sharing syringes (needles) to use any drug can lead to negative health effects. These include increased likelihood of other bacterial infections, such as a heart infection called infective endocarditis, as well as getting sick from a virus, such as HIV or hepatitis C.

Because xylazine emerged as a factor in the overdose crisis recently, the national scope of overdose deaths involving xylazine is unknown. It first appeared in the drug supply in Puerto Rico in the early 2000s. From 2019 to 2022, xylazine detection more than doubled in 30 states, according to data on drug seizures in those states.⁸ The U.S. Centers for Disease Control and Prevention’s (CDC) State Unintentional Drug Overdose Reporting System (SUDORS) reported that in 20 states and the District of Columbia, the monthly percentage of fentanyl-related overdose deaths with xylazine detected increased 276% from January 2019 (2.9%) to June 2022 (10.9%). Rates may vary by state, though. One study of fatal overdoses in Michigan found that xylazine was present in 4.7% of fatal overdoses in 2023.⁹

However, early research does not indicate that xylazine combined with opioids increases odds of fatal overdose. NIDA-funded research found that people with xylazine and fentanyl in their systems at the time of overdose had lower rates of heart attack and coma than those who tested positive for opioids alone.¹⁰ The same study found that people with xylazine in their bodies at the time of opioid overdose were no more likely to die than people who had an opioid overdose but no xylazine in their systems. People with opioid overdose plus xylazine exposure also were no more likely to be admitted to the hospital and did not stay in the hospital longer than people who used opioids without xylazine.⁸

Another study found that people with fentanyl and xylazine in their systems at the time of opioid overdose were no more likely to receive the overdose reversal medication naloxone and were more likely to have a pulse when emergency responders arrived than those with fentanyl but without xylazine.¹¹ NIDA supports research to understand these findings, including understanding how xylazine affects fentanyl in the body, and whether these early findings can be confirmed.

Opioid overdose reversal medications such as naloxone and nalmafene do not reverse xylazine’s effects. But experts recommend giving them because xylazine overdoses almost always include opioids and other drugs. In an emergency, call 9-1-1 or other emergency services immediately for care after administering an opioid overdose reversal medication. If the person is unconscious, check that they continue to breathe. Place them on their side with their head supported. If they stop breathing, give rescue breaths if you can. If possible, stay with the person until emergency services arrive.

To be diagnosed with a substance use disorder, a person must meet specific diagnostic criteria for continued, compulsive substance use despite negative consequences. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)—a reference text published by the American Psychiatric Association that health professionals use to diagnose substance use disorders and other psychiatric disorders—does not include a specific diagnosis related to xylazine.¹² However, early research suggests substance use disorder symptoms and withdrawal symptoms may be more intense for those taking xylazine with fentanyl versus fentanyl alone.^13,14 More research is needed to understand this finding and the addictive potential of xylazine. NIDA conducts and supports research to better understand how often and to what extent people who use xylazine experience withdrawal and substance use disorder symptoms.

Xylazine-related skin wounds can include skin infections, wounds below the skin (abscesses) and open, weeping wounds (skin ulcers). Wounds can heal if a person continues to use substances and receives appropriate medical care. However, early data indicates that healing is slower if a person continues to use substances containing xylazine.¹⁵  These wounds can be painful, and severe wounds may require pain treatment and admission to a hospital.¹² If untreated or undertreated, these infections can lead to amputation of the infected body part.

Medical associations have not created guidelines for how to treat xylazine-associated wounds. However, wounds should be kept clean. Early evidence suggests keeping the wounds clean but open (without stitches or skin grafts). NIDA supports research to better understand how to treat xylazine-related wounds.

Harm reduction approaches can help people who use drugs reduce some of the harms of xylazine, including:

• Carry overdose reversal medications like naloxone and nalmafene in case of opioid overdose. Overdose reversal medications do not reverse the effects of xylazine. However, illicitly manufactured xylazine is most often found mixed with opioids like fentanyl. So experts recommend giving opioid overdose reversal medications to someone who shows symptoms of an overdose, even if you know that xylazine is present.
• Check drugs for the presence of xylazine, where available. Research shows that illicitly manufactured xylazine is almost always mixed in with other drugs. So checking drugs for xylazine can provide a person with more complete information. For the same reason, people may want to check their drugs for the presence of fentanyl. Xylazine test strips are now commercially available, as well as accessible at some harm reduction organizations. Harm reduction organizations may also have machines that can check drugs for the presence of xylazine.
• Use sterile syringes and avoid reusing or sharing syringes.
• Monitor and treat wounds. Wounds and skin infections associated with xylazine can quickly lead to serious health problems. Find out if local harm reduction organizations provide wound care or wound-care kits. Monitor injection sites or other wounds and seek prompt medical attention if the infection gets worse or does not heal.

As a veterinary medication, xylazine is not FDA-approved for any human use. It is not currently a controlled substance under the federal Controlled Substances Act. Some states have placed xylazine on their own controlled substances lists. The FDA also took action in early 2023 to restrict unlawful import of xylazine and the ingredients necessary to make xylazine.

By itself, xylazine may be known as “tranq.” When it is combined with opioids such as fentanyl, it may be called “tranq dope.” Some terms used for xylazine reflect the stigma directed at people who use drugs, such as “zombie drug.” Learn more about accurate, stigma-free language related to drug use at Words Matter: Preferred Language for Talking About Addiction.

NIDA supports pre-clinical and clinical research into human use of xylazine. This includes funding research that studies:

• The state of xylazine in the drug supply and its health effects. These include how often people use xylazine on purpose versus by accident in other drugs and how common xylazine-related skin and muscle wounds are.
• The effect of xylazine on fentanyl addiction, ways to understand and treat xylazine-related overdoses, as well as potential withdrawal from xylazine.
• Community-based solutions to the presence of xylazine in local drug supplies.

NIDA supports research to better understand how xylazine impacts individual and public health. Finally, NIDA supports programs that track and understand emerging drug use patterns and changes to the drug supply across the United States, including xylazine.