Classification: Central nervous system (CNS) depressant

Background: Xylazine is an FDA-approved veterinary tranquilizer and is not approved for human use. It has been investigated as an antihypertensive agent and analgesic, anesthetic, hypnotic agent. Findings included severe hypotension and CNS depression and trials were terminated.

Abuse of xylazine was first noted in the early 2000’s and more recently it has entered the US illicit drug supply as an adulterant. Reasons for its incorporation as an adulterant are unclear but likely stem from its low cost and the “boost” it provides to other centrally active drugs such as heroin, fentanyl, or cocaine.

Prescribed as: Rompun, Anased, Sedazine, Chanazine for veterinary use only. Not approved for human use.

Street Names: Tranq, tranq-dope

Modes of Use: Smoked, Intravenous, intranasal and oral.

Physiological / Psychological Effects: Can cause drowsiness, amnesia, and slow breathing, heart rate and blood pressure at dangerously low levels. At very high doses, or with other central nervous system depressants, it can cause loss of physical sensation, loss of consciousness, and intensification of the effects of other drugs, which can complicate overdose presentation and treatment. May cause skin and soft tissue wounds, including ulcerations.

Toxicity: Respiratory and CNS depression, hypotension, bradycardia, hypothermia, miosis. Substantially similar to the toxic effects of opioids. When used in combination with opioids, a synergistic effect is noted. Xylazine has been documented to produce a dependence in users and a classic withdrawal syndrome following abstinence. Notable for users entering an opioid treatment program as traditional medications such as methadone or buprenorphine may not provide adequate relief.

In the event of an overdose, health professionals recommend using the opioid antagonist, naloxone. Naloxone will not reverse the effects of xylazine, but it will block the effects of opioids, which are almost always reported in cases of xylazine overdose. Concern has been raised about the efficacy of naloxone in overdose cases as the percentage of xylazine as an adulterant increases.

Metabolism: Data on xylazine metabolism is limited. Several oxidative and hydroxylated metabolites are expected due to biotransformation. However, following xylazine use, parent xylazine is detected in appreciable concentrations.    

Detection Time in Urine: Pharmacokinetic data on the fate of xylazine in humans is limited. Preliminary studies suggest a urinary detection window of 1–7 days.