Product Code Database
Xylazine is a structural analog of clonidine and an α2-adrenergic receptor agonist, sold under many trade names worldwide, most notably the Bayer brand name Rompun, as well as Anased, Sedazine and Chanazine.
Xylazine is a common veterinary drug used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle, and other mammals. In veterinary anesthesia, it is often used in combination with ketamine. Veterinarians also use xylazine as an emetic, especially in cats. vary with different animals.
Xylazine was first investigated for human use in the 1960s in West Germany for antihypertensive effects before being discontinued and marketed as a veterinary sedative. Xylazine’s mechanism of action was discovered in 1981, which led to the creation of other α2-adrenergic receptor agonists such as medetomidine and dexmedetomidine.
Xylazine has become a commonly substance abuse street drug in the United States where it is known by the street name " tranq", particularly in the territory of Puerto Rico. The drug is used as a cutting agent for heroin and fentanyl.
In the United States, xylazine was approved by the FDA only for veterinary use as a sedative, analgesic, and muscle relaxant in dogs, cats, horses, elk, fallow deer, mule deer, sika deer, and white-tailed deer. The sedative and analgesic effects of xylazine are related to central nervous system depression. Xylazine's muscle relaxant effect inhibits the transmission of neural impulses in the central nervous system.
In scientific research using animal experiments, xylazine is a component of the most common anesthetic, ketamine-xylazine , to anesthetize rats, mice, hamsters, and guinea pigs.
Xylazine has not previously been a controlled substance; however, due to illicit abuse of xylazine legislative restrictions have been proposed in multiple countries. Xylazine was made a class C drug in the UK on 15 January 2025.
Xylazine's use in cats and dogs is being replaced with the more selective alpha2 adrenergic receptor agonists medetomidine and dexmedetomidine and in some countries xylazine is rarely used with cats and dogs.
High amounts of in a patient will require higher doses of xylazine to be administered to provide sedation. The heightened levels required may not be practical or possible to administer and regular doses may cause excitement.
Xylazine has been demonstrated as reducing the dose of epinephrine that causes arrythmia in dogs anaesthetised with isoflurane and halothane.
Xylazine administration in sheep activates pulmonary macrophages that damage the capillary endothelium and alveolar type I cells. This in turns causes alveolar haemorrhage and oedema causing hypoxaemia.
Intracarotid administration can cause seizures and excitement in horses.
Xylazine has been shown to cause myometrial contractions in pregnant cattle. Further evidence of xylazine's effect on pregnant animals is lacking and although other a2 adrenergic receptor agonists have been shown to not cause the same myometrial contraction the administration of a2 adrenergic receptor agonists is not recommended and should only be used in specific circumstances for animals near-term.
Xylazine affects the glucose level via the activation of alpha2A andrenergic receptors on beta cells, which prevents insulin release. alpha2 adrenergic receptors have been reported to cause transient hyperglycaemia with xylazine being reported as a cause in cattle and equine. The renal threshold for glucose is not exceeded due to the hyperglycaemia with clinical doses. An alpha2 adrenergic receptor antagonist can reverse the effect.
Emesis is the most common side effect in small animals; however, this can be a desired effect and xylazine is often used as an emetic in cats. (2026). 9780323244855, Elsevier. ISBN 9780323244855
Xylazine is contraindicated for pregnant animals as it impairs oxygen and blood circulation to the fetus and it can induce parturition
Xylazine is a potent α2-adrenergic receptor agonist. When xylazine and other α2-adrenergic receptor agonists are administered, they distribute throughout the body within 30 to 40 minutes. Due to xylazine's highly lipophilic nature, it directly stimulates central α2-adrenergic receptors as well as peripheral α-adrenergic receptors in a variety of tissues. As an agonist, xylazine reduces release of norepinephrine in the central nervous system. It does so by mimicking norepinephrine in binding to the pre-synaptic surface , which leads to feedback inhibition of norepinephrine release. Recent data suggests that xylazine treatment can induce dopamine release in the nucleus accumbens through an unresolved mechanism, and this effect is blocked by atipamezole.
Xylazine also serves as a transport inhibitor by suppressing norepinephrine transport function through competitive inhibition of substrate transport. Accordingly, xylazine significantly increases Km and does not affect Vmax. This likely occurs by direct interaction on an area that overlaps with the antidepressant binding site. For example, xylazine and clonidine suppress uptake of iobenguane (MIBG), a norepinephrine analogue, in neuroblastoma cells. Xylazine's chemical structure closely resembles clonidine.
It has also been reported that xylazine activates the κ-opioid receptors, with low potency, which may contribute to its effects.
Unlike other α2-adrenergic receptor agonists xylazine does not have any imidazoline receptor activity. Xylazine binds at a ratio of 160:0, the lowest of all α2-adrenergic receptor agonists and 1/10th of that of medetomidine and dexmedotimidine.
Xylazine is less selective than the other α2-Adrenergic receptor agonists.
The analgesic effect of xylazine comes from binding to receptors at the substantia gelatinosa and locus coeruleus.
Xylazine's action can be seen usually 15–30 minutes after administration and the sedative effect may continue for 1–2 hours and last up to 4 hours. Once xylazine gains access to the vascular system, it is distributed within the blood, allowing xylazine to enter the heart, lungs, liver, and kidney. In non-fatal cases, the blood plasma concentrations range from 0.03 to 4.6 mg/L. Xylazine diffuses extensively and penetrates the blood–brain barrier, as might be expected due to the uncharged, lipophilic nature of the compound.
Xylazine is metabolized by the liver's cytochrome P450 enzymes. When it reaches the liver, xylazine is metabolized and proceeds to the kidneys to be excreted in urine. Around 70% of a dose is excreted unchanged. Thus, urine can be used in detecting xylazine administration because it contains many , which are the main targets and products in urine. Within a few hours, xylazine decreases to undetectable levels. Other factors can also significantly impact the pharmacokinetics of xylazine, such as sex, nutrition, environmental conditions, and prior diseases.
| +Xylazine metabolites |
| Xylazine-M (sulfone-HO-) isomer 2 |
| Xylazine M (oxo-) |
| Xylazine-M (HO-) isomer 2 |
| Xylazine-M (HO-oxo-) isomer 1 glucuronide |
| Xylazine-M (sulfone) |
Xylazine is not regulated as a controlled substance under the Controlled Substances Act. It is sold online through distributors often without requiring proof of a veterinary license. As a commonly used veterinary medicine xylazine is probably diverted from veterinary sources. The cost to purchase Xylazine from overseas suppliers is around $6–20 per kilogram. This low price makes it attractive for dealers looking for a cheap additive that is addictive and not treatable with opiate withdrawal medications. The withdrawal can last for two weeks and has a quicker onset than fentanyl.
Xylazine is most commonly ingested as an additive with fentanyl. Xylazine has also been reported in combination with medetomidine, another potent α2-adrenergic receptor agonist. It is unknown if drug users are ingesting it knowingly. As of 2024, Seattle police report that some users wrongly believe they are consuming higher-quality fentanyl. Xylazine's street name in Puerto Rico is anestesia de caballo, which translates to "horse anesthetic". From 2002 to 2008, its use was associated with a high number of inmate deaths at the Guerrero Correctional Institution in Aguadilla, Puerto Rico.
Xylazine's street name in the United States, particularly when it is mixed with fentanyl, is "tranq", "tranq dope" and "zombie drug".
As of 2012, xylazine users in Puerto Rico were more likely to be male, under age 30, living in a rural area, and injecting rather than inhaling xylazine. The combination of heroin and xylazine produces a potentially more deadly high than administration of heroin alone. Xylazine is also frequently found in "speedball", a mixture of a stimulant drug such as cocaine with a depressant drug such as heroin, morphine and/or fentanyl. As of 2012, causal factors underlying xylazine's increasing popularity were still unknown.
As of 2022, more information on the distribution of xylazine in the body, physical symptoms, and factors predictive of chronic use was known: when used, frequency of use depended on social or economic factors, as well as each user's subjective response to the drug's addictive properties. From November 2021 until August 2022, 80% of drug paraphernalia which tested positive for fentanyl at needle exchange programs in Maryland also contained xylazine. As of 2022, xylazine was almost invariably combined with when used recreationally, and the drug produced a characteristic withdrawal syndrome which complicates treatment of addicted users.
In April 2023, the Biden administration declared xylazine-laced fentanyl an official emerging drug threat to the nation, the first time such a label has been given. According to Gupta, xylazine is the deadliest drug threat the United States has ever faced. The Drug Enforcement Administration (DEA) has seized xylazine and fentanyl mixtures in most states, finding 23% of seized fentanyl powder and 7% of fentanyl pills adulterated with xylazine.
In July 2023, the first death following xylazine use outside of North America was reported to have taken place in Solihull, England on May 22. A 43-year-old male was found dead at home with postmortem toxicology detecting heroin, cocaine, fentanyl and xylazine.
The most common in humans associated with xylazine administration include bradycardia, respiratory depression, hypotension, transient hypertension secondary to α1-adrenergic receptor stimulation, and other central and hemodynamic changes. Xylazine significantly decreases heart rate in animals that are not pre-medicated with medications that have anticholinergic effects.
Other possible side-effects are areflexia, asthenia, ataxia, blurred vision, disorientation, dizziness, drowsiness, dysarthria, dysmetria, fainting, hyporeflexia, slurred speech, somnolence, staggering, coma, apnea, shallow breathing, sleepiness, premature ventricular contraction, tachycardia, miosis and dry mouth. Rarely, hypotonia, urinary incontinence, and nonspecific electrocardiographic ST segment changes occur. Following a human overdose, symptoms can last for 8–72 hours, varying based on xylazine's combined usage with other drugs.
Hemodialysis has been suggested as a form of treatment, but is usually unfavorable due to the large volume of distribution of xylazine.
There are no standardized screenings to determine if an overdose has occurred. Detection of xylazine in humans involves various screening methods, such as urine screenings, thin layer chromatography (TLC), gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS). As of November 2022, detecting xylazine in a drug sample requires spectrophotometry.
, the α2-adrenergic receptor antagonist atipamezole was used to reverse the effects of xylazine or the related drug dexmedetomidine in veterinary medicine, but this is not an approved medical treatment for humans, despite Phase I clinical trials in 2005.
the effects of xylazine in animals were also reversed by the [[analeptic]]s 4-aminopyridine, [[doxapram]], and [[caffeine]], which are physiological antagonists to central nervous system depressants. The ways to accurately identify chronic xylazine usage are unknown, and the effective treatments, if any, are not standardized. multiple drugs have been used for therapeutic intervention, including [[lidocaine]], [[naloxone]], [[thiamine]], [[lorazepam]], [[vecuronium]], [[etomidate]], [[propofol]], [[tolazoline]], [[yohimbine]], [[atropine]], [[orciprenaline]], [[metoclopramide]], [[ranitidine]], [[metoprolol]], [[enoxaparin]], [[flucloxacillin]], [[insulin]], and irrigation of both eyes with saline.
The treatment after a xylazine overdose primarily involves maintaining respiratory function and blood pressure. In cases of intoxication, physicians recommend intravenous fluid infusion, atropine, and hospital observation. Severe cases may require tracheal intubation, mechanical ventilation, gastric lavage, activated charcoal, bladder catheterization, electrocardiographic (ECG) and hyperglycemia monitoring. Physicians typically recommend which detoxification treatment should be used to manage possible dysfunction involving highly perfusion organs such as the liver and kidneys.
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