Xylazine is an alpha-adrenergic receptor agonist approved for use only in animals with a prescription from a veterinarian. It is a powerful sedative that is slowly infiltrating the recreational street drug scene and is often used by polysubstance abusers. Known as "tranq," it can be fatal, and xylazine-induced toxicity cannot be reversed with naloxone or nalmefene. Due to its vasoconstrictive effects, chronic use of xylazine is associated with necrotic skin lesions and general deterioration of health. Since xylazine is not approved for human use and is not scheduled as a controlled substance, there are no human studies to provide evidence of drug-drug interactions, lethal doses, or reversal protocols. Xylazine is available online without a prescription. Street drug users may take xylazine knowingly or unknowingly, as it is often combined with other illicit substances such as fentanyl. There are no rapid tests for xylazine, although there are specialty tests that can be ordered. Xylazine represents a major threat to street drug users and another challenge to emergency healthcare workers, first responders, and others who care for those who have taken this "new" street drug.