Photo of a prescription bottle full of and surrounded by counterfeit pills.

On May 2, Boulder County issued a press release in partnership with the Boulder County Drug Task Force and Boulder County Public Health (BCPH) to notify residents that xylazine is being distributed in the county’s illicit drug supply. They are urging residents to take extra precautions to stay safe.

Additionally, the White House Office of National Drug Control Policy (ONDCP), designated fentanyl adulterated or associated with xylazine as an emerging threat to the United States. This designation comes after careful review of the impact of xylazine on the opioid crisis, including its growing role in overdose deaths in every region of the United States.

Even if you don't use substances, the following information can help you provide support for students, colleagues and community members.

Here are four things everyone should know about xylazine.

1. What is xylazine?


Photo of a vial of xylazine next to its packaging box.Xylazine (also known as ‘tranq’ or ‘zombie drug’) is a non-opioid veterinary tranquilizer that is most commonly used to sedate horses. While it is FDA-approved for use in animals, it is not safe for use in humans and can result in serious, life-threatening side effects. 

Xylazine is often mixed into fentanyl, but it has also been detected in other substances, including cocaine and counterfeit prescriptions.

While xylazine is not an opioid, it is considered a central nervous system depressant that causes drowsiness, amnesia, slow breathing and low heart rate and blood pressure. When used with opioids, benzodiazepines or alcohol, xylazine can lead to a fatal overdose. 

*Please note: Those who inject substances containing xylazine can develop severe skin wounds and patches of necrotic tissue that can easily become infected and, if left untreated, can be life-threatening. These wounds can develop in areas of the body away from the injection site.

2. Why is xylazine so dangerous?

When combined with fentanyl or other synthetic opioids, xylazine can increase the potential for fatal overdoses. In 2022, the U.S. Drug Enforcement Administration (DEA) reported that approximately 23% of all fentanyl powder and 7% of all counterfeit fentanyl pills seized contained xylazine. 

Xylazine and fentanyl drug mixtures, which can be sold as counterfeit prescriptions, put users at increased risk of suffering a fatal drug overdose. It can also be difficult to distinguish genuine pills from fake versions.

Xylazine can mimic the side effects seen in opioid overdoses, making it difficult to distinguish whether or not someone is overdosing from xylazine. Additionally, there is no approved antidote to treat xylazine overdoses in humans.

In the event of a suspected overdose, it’s important to administer naloxone because xylazine is often combined with opioids like fentanyl. However, because xylazine is not an opioid, naloxone will not reverse the effects of xylazine. If you suspect that someone may be suffering from an opioid or xylazine overdose, always call 911 to request emergency medical services.

3. How common is it?

Xylazine is not currently considered a controlled substance under the U.S. Controlled Substances Act. For this reason, xylazine may be more readily available for drug traffickers to purchase compared to other substances or drug precursors. 

While the scope of xylazine overdoses, deaths and distribution is largely unknown, the DEA has reported an increased prevalence of xylazine across the United States. Because xylazine is not typically included in routine toxicology tests, it may also be under-detected or under-accounted for in overdose cases and other life-threatening events. 

4. Tips for staying safe

The best way to reduce your risk of an accidental overdose is to avoid using any substance that is not directly prescribed to you by a healthcare provider. However, if you choose to use prescription medications or illicit drugs, there are ways to prevent accidental overdoses. 

*Please note:  Due to the unpredictability of fentanyl and xylazine, there is no foolproof way to eliminate the risk of overdose. 

Tip: Know what you’re getting into

Assume that any pill or drug not purchased directly from a pharmacy could contain fentanyl, xylazine or both. This includes illicit drugs (cocaine, heroin, meth, etc.) as well as counterfeit prescription medications (Xanax, Oxy, Percocet, Adderall, etc.).

Tip: Keep naloxone on hand

Naloxone is an FDA-approved medication that can be used to temporarily reverse opioid overdoses. Naloxone is typically administered through a nasal spray, but it also comes in an injectable form. This medication can help temporarily reverse opioid overdoses, but it can wear off quickly or require additional doses for fentanyl.

While naloxone will not reverse the effects of xylazine, it is important to administer it whenever you suspect someone may be experiencing an overdose, as there may be unknown opioids contributing to the overdose. All CU Boulder students, staff and faculty can pick up free naloxone from Health Promotion on the third floor of Wardenburg Health Center.

Learn more about naloxone and how to use it

Tip: Be prepared to call for help

Be prepared to call 911 in a potential overdose situation.

Here are some signs to look for and how to respond to a potential overdose.

Signs of an overdose

  • Sudden drowsiness
  • Unresponsive, passed out
  • Reduced heart rate
  • Shallow or no breathing
  • Pinpoint (small) pupils
  • Blue or grayish lips/fingernails
  • Gurgling/heavy wheezing or snoring sound

​ How to respond

  • Call 911 and stay with the person until help arrives
  • Check to make sure they are breathing and have a pulse
  • Administer naloxone
  • Try to get their attention and/or wake them up
  • Perform rescue breaths by laying them on their back, pinching their nose closed and blowing breaths into their mouth
  • Place them in the recovery position

Important policies to know

CU Boulder Amnesty Policy

Calling for help in an alcohol- or drug-related emergency means neither the person who calls for help nor the person who needs help will be subject to formal disciplinary sanctions by the university (i.e., probation, suspension, expulsion).   

To be covered by the Amnesty Policy, a student must:  

  • Call for help (911 or university staff). 
  • Stay with the individual until help arrives. 
  • Cooperate with staff and emergency responders. 

911 Good Samaritan Law

The 911 Good Samaritan Law states that a person is immune from criminal prosecution for an offense when the person reports, in good faith, an emergency drug or alcohol overdose even to a law enforcement officer, to the 911 system or to a medical provider.  

This same immunity applies to persons who remain at the scene of the event until a law enforcement officer, or an emergency medical responder arrives, or if the person remains at the facilities of the medical provider until a law enforcement officer, emergency medical responder or medical provider arrives. The immunity described above also extends to the person who suffered the emergency drug or alcohol overdose event.


Tip: Avoid using substances alone

If you can’t be in the company of someone else who is sober, plan to have someone check in on you in case you need help. If you are with friends who are also using, have someone else check in on all of you. It’s also important to have naloxone on hand. Ensure that everyone knows where to access it and how to use it in case of an emergency.

There are also overdose prevention apps available. Individuals are encouraged to explore this as an option and determine if there is one that seems like a good fit.

Tip: Start small and go slow

Start with a very small dose every time you use something that could be contaminated with fentanyl, xylazine or other substances. The amount of these substances present in a single pill or drug can vary widely. One pill may be contaminated, and the next may not be.

Test for fentanyl

Students, staff and faculty can pick up free fentanyl test strips from Health Promotion on the third floor of Wardenburg Health Center. While testing for fentanyl can reduce harm, it does not guarantee safety. It's possible that fentanyl is present in an untested area or that the pill contains a different substance (like xylazine) or a different synthetic opioid.

*Please note: Fentanyl test strips will not detect xylazine. However, xylazine is often present in combination with fentanyl.

Tip: Sobriety can reduce tolerance

If you’ve used fentanyl, xylazine or other substances in the past and have recently experienced a period of sobriety, your tolerance for the drug has likely decreased. If you choose to use again, be mindful of potential changes in drug potency and start with a smaller dose than you may have used in the past. Changes in tolerance can increase the likelihood of unwanted experiences, including overdose.

Campus resources

There are resources available to support students, staff, faculty and families at CU Boulder.

Community resources

Students, staff, faculty and community members can also access resources outside the university.

  • Boulder Works Program
    • The Works Program is a free, legal and anonymous harm reduction program that provides free supplies, disposal programs and referrals. Their goal is to reduce the rsiks of disease and overdose deaths across Boulder County communities.
  • Stop the Clock
    • There is a fatal overdose in Colorado every 4 hours, 45 minutes and 9 seconds. Stop the Clock connects community members with pharmacies and other sites that offer naloxone.
  • Boulder County Substance Use Advisory Group
    • The Substance Use Advisory Group is working toward preventing fatal overdoses, destigmatizing substance use disorders (SUDs), promoting harm reduction and supporting affected individuals into treatment and recovery.
  • Substance use hotline
    • The Substance Abuse and Mental Health Services Administration (SAMHSA) offers a free, confidential, 24/7 treatment referral and information hotline for individuals and families facing mental health and/or substance use disorders.