Xylazine Exposures Reported to Texas Poison Centers

Qualitative and quantitative determination of xylazine in oral fluid

Xylazine has emerged in recent years as a dangerous adulterant in illicit fentanyl use, and methods for the detection of xylazine in toxicology panels are still lagging. We developed methods for the screening and quantitation of xylazine in oral fluid (OF), a popular testing medium due to its ease of collection and reflection of presence in blood for many classes of drugs. Enzyme-linked immunosorbent assays were employed for the rapid screening of xylazine directly from the collection device buffer with a cutoff of 1 ng/mL. Solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry facilitated the confirmation and quantification of xylazine as low as 0.1 ng/mL and a dynamic range of 0.1-25 ng/mL. Selectivity, ionization suppression, processed sample stability, and dilution effect were also assessed. The method was validated through the American National Standards Institute/American Academy of Forensic Sciences Standards Board (ANSI/ASB) Standard 036, first edition from 2019, and found to be accurate, precise, and robust. Living human subject OF samples collected within substance use disorder and therapeutic drug monitoring clinics received between September 2023 and January 2024, with the specific request to test for xylazine (n = 57), were screened. Presumptive positive samples were confirmed using the validated method. Xylazine confirmed living human subject OF sample concentrations ranged from 1.2 to 23.3 ng/mL.

Classics in Chemical Neuroscience: Xylazine

Xylazine (also known as "tranq") is a potent nonopioid veterinary sedative that has recently experienced a surge in use as a drug adulterant, most often combined with illicitly manufactured fentanyl. This combination may heighten the risk of fatal overdose. Xylazine has no known antidote approved for use in humans, and age-adjusted overdose deaths involving xylazine were 35 times higher in 2021 than 2018. In April 2023, the Biden Administration declared xylazine-laced fentanyl an emerging drug threat in the United States. In 2022, the Drug Enforcement Agency (DEA) reported nearly a quarter of seized fentanyl powder contained xylazine. This dramatic increase in prevalence has solidified the status of xylazine as an emerging drug of abuse and an evolving threat to public health. The following narrative review outlines the synthesis, pharmacokinetics, pharmacodynamics, and adverse effects of xylazine, as well as the role it may play in the ongoing opioid epidemic.

Xylazine-Associated Wounds and Related Health Concerns Among People Who Use Drugs: Reports From Front-Line Health Workers in 7 US States

BACKGROUND

Xylazine, an adrenergic alpha-2 agonist increasingly present in the US drug supply, is associated with severe skin ulcers and other harms. Expert knowledge from front-line harm reduction and healthcare professionals is an essential component of evidence-based practice. The purpose of this study is to describe the progression and treatment of xylazine-associated wounds, other xylazine-related health concerns, and the most urgent research priorities as reported by front-line harm reduction and healthcare professionals serving people who use drugs.

METHODS

A convenience sample of 17 healthcare and harm reduction professionals who serve people who use drugs in the US states of Maryland, Massachusetts, Michigan, Minnesota, North Carolina, Pennsylvania, and Texas participated in semi-structured interviews. Participants were asked about the appearance and progression of xylazine-associated wounds; preferred treatment strategies; other xylazine-related harms experienced by people who use drugs; and the most urgent priorities for xylazine-related research.

FINDINGS

Xylazine-associated wounds were broadly described as small lesions appearing mostly on extremities both at and away from injection sites, often within hours or days of exposure, that quickly developed into large, complex, chronic wounds. Reported risk of secondary infection was generally low but appeared more common among unhoused populations. Most participants preferred conservative treatment strategies that included regular wound care, enzymatic debridement, and hygiene. Xylazine-associated wounds and xylazine withdrawal reportedly act as significant barriers to care, including addiction treatment. Participants reported urgent need for scientific research and evidence-based guidance on the management of xylazine-associated wounds and withdrawal.

CONCLUSIONS

High-quality scientific evidence on risk factors for xylazine-associated wounds and on their biologic mechanisms is needed. Such studies could inform new strategies for the prevention and treatment of these wounds. Efforts to improve the management of xylazine withdrawal and to reduce stigma by incorporating harm reduction professionals into healthcare settings may improve access to and retention in care.

Xylazine Poisoning in Clinical and Forensic Practice: Analysis Method, Characteristics, Mechanism and Future Challenges

Xylazine abuse is emerging globally, while the identification of xylazine lethal cases poses a great challenge in clinical and forensic practice. The non-specific symptoms delay the diagnosis and treatment of xylazine poisoning, the pathological changes and lethal concentration of xylazine in body fluid and organs of fatal xylazine poisoning cases are seldom reported and the other toxins detected in such cases complicate the role of xylazine in the cause of death. Therefore, we carefully reviewed related updated information on xylazine, summarized the knowledge from clinical and forensic perspectives and can thus provide a reference in such cases and throw light on further study in the field of xylazine poisoning.

Widespread Distribution of Xylazine Detected Throughout the United States in Healthcare Patient Samples

OBJECTIVES

Xylazine is a tranquilizer commonly added into the illicit drug supply and a likely contributor to overdoses because it does not respond to naloxone reversal. The objective of this study was to perform a retrospective data analysis on xylazine-positive samples collected from patients in various outpatient healthcare settings to illustrate geographic distribution and common copositive substances, which may also contribute to risk of adverse events.

METHODS

Samples for which providers ordered testing for xylazine were subjected to enzymatic hydrolysis, extracted, and analyzed using liquid chromatography-tandem mass spectrometry. Retrospective analysis was performed on xylazine-positive samples collected from April 2021 to March 2022, to include geographic location and copositive substances.

RESULTS

Xylazine was identified in 413 of 59,498 samples from adults aged 20-73 years and originated from 25 of the 39 states where xylazine testing was ordered. The most common routine substances detected with xylazine were fentanyl, buprenorphine, naloxone, cocaine, d -methamphetamine, and delta-9-tetrahydrocannabinol. The most common designer drugs detected included fentanyl analogs, isotonitazene, and designer benzodiazepines.

CONCLUSIONS

Xylazine is geographically spread throughout the United States, indicative of a wide incorporation into the illicit drug supply. These findings differ from previous studies in that these samples originated from healthcare providers in routine care settings, where other reports typically involve overdose deaths. This analysis illustrates that routine testing for xylazine in outpatient settings can afford providers the opportunity to educate individuals and adjust harm reduction measures to potentially mitigate overdose risk.

The New Stealth Drug on the Street: A Narrative Review of Xylazine as a Street Drug

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.

Opioid overdoses involving xylazine in emergency department patients: a multicenter study

INTRODUCTION

Illicit opioids, consisting largely of fentanyl, novel synthetic opioids, and adulterants, are the primary cause of drug overdose fatality in the United States. Xylazine, an alpha-2 adrenergic agonist and veterinary tranquilizer, is being increasingly detected among decedents following illicit opioid overdose. Clinical outcomes in non-fatal overdose involving xylazine are unexplored. Therefore, among emergency department patients with illicit opioid overdose, we evaluated clinical outcome differences for patients with and without xylazine exposures.

METHODS

This multicenter, prospective cohort study enrolled adult patients with opioid overdose who presented to one of nine United States emergency departments between 21 September 2020, and 17 August 2021. Patients with opioid overdose were screened and included if they tested positive for an illicit opioid (heroin, fentanyl, fentanyl analog, or novel synthetic opioid) or xylazine. Patient serum was analyzed via liquid chromatography quadrupole time-of-flight mass spectroscopy to detect current illicit opioids, novel synthetic opioids, xylazine and adulterants. Overdose severity surrogate outcomes were: (a) cardiac arrest requiring cardiopulmonary resuscitation (primary); and (b) coma within 4 h of arrival (secondary).

RESULTS

Three hundred and twenty-one patients met inclusion criteria: 90 tested positive for xylazine and 231 were negative. The primary outcome occurred in 37 patients, and the secondary outcome occurred in 111 patients. Using multivariable regression analysis, patients positive for xylazine had significantly lower adjusted odds of cardiac arrest (adjusted OR 0.30, 95% CI 0.10-0.92) and coma (adjusted OR 0.52, 95% CI 0.29-0.94).

CONCLUSIONS

In this large multicenter cohort, cardiac arrest and coma in emergency department patients with illicit opioid overdose were significantly less severe in those testing positive for xylazine.

Xylazine: Pharmacology Review and Prevalence and Drug Combinations in Forensic Toxicology Casework

Xylazine, an alpha-2 receptor agonist used in veterinary medicine for its sedative and muscle relaxant effects, has been reported in forensic toxicology casework since the 1980s. It is not approved for human use, but it is used as an adulterant in heroin and illicit fentanyl. The prevalence and concentrations of xylazine in 2.5 years (January 2019-June 2021) of driving-under-the-influence-of-drugs (DUID) and medical-death-investigation (MDI) cases was investigated, including other drugs detected in combination with xylazine. Of over 170,000 cases screened for xylazine, 97% were classified as MDI. Over the course of the study period the prevalence and geographical spread of xylazine increased. Overall, 2.8% of DUID and 2.1% of MDI cases screened positive for xylazine with concentrations of 5.1-450 ng/mL (mean = 36 ng/mL) and 5.0-11,000 ng/mL (mean = 41 ng/mL), respectively. Two MDI cases which had xylazine concentrations of 9,100 and 11,000 ng/mL were drug overdose suicides that did not involve any opioids. Opioids, primarily fentanyl and/or a fentanyl byproduct/metabolite were detected in 100% of DUID and all but two MDI cases. After opioids, stimulants, phyto-cannabinoids and benzodiazepines were the most common drug classes detected in conjunction with xylazine in both DUID and MDI casework. In summary, xylazine exposure continues to increase, mostthrough the adulteration of illicit opioids. There is extensive overlap in the concentrations between living and deceased individuals making it difficult to interpret the role of the drug in MDI or DUID cases without other case information.

Vortex-assisted dispersive liquid-liquid microextraction-gas chromatography (VADLLME-GC) determination of residual ketamine, nimetazepam, and xylazine from drug-spiked beverages appearing in liquid, droplet, and dry forms

Presently, investigations of drug-facilitated crimes (DFCs) rely on the detection of substances extracted from biological samples following intake by the victim. However, such detection requires rapid sampling and analysis prior to metabolism and elimination of the drugs from the body. In cases of suspected DFCs, drug-spiked beverage samples, whether in liquid, droplet, or even dried form, can be tested for the presence of spike drugs and used as evidence for the occurrence of DFCs. This study aimed to quantitatively determine three sedative-hypnotics (ketamine, nimetazepam, and xylazine) from drug-spiked beverages using a vortex-assisted dispersive liquid-liquid microextraction-gas chromatography (VADLLME-GC) approach. In this study, a GC method was first developed and validated, followed by the optimization of the VADLLME protocol, which was then applied to quantify the target substances in simulated forensic case scenarios. The developed GC method was selective, sensitive (limit of detection: 0.08 μg/ml [ketamine]; 0.16 μg/ml [nimetazepam]; 0.08 μg/ml [xylazine]), linear (R²  > 0.99), precise (%RSD <7.2%), and accurate (% recovery: 92.8%-103.5%). Higher recoveries were achieved for the three drugs from beverage samples in liquid form (51%-97%) as compared to droplet (48%-96%) and dried (44%-93%) residues. The recovery was not hindered by very low volumes of spiked beverage and dried residues. In conclusion, the developed VADLLME-GC method successfully recovered ketamine, nimetazepam, and xylazine from spiked beverages that are likely to be encountered during forensic investigation of DFCs.

Nanocoral-like Polyaniline-Modified Graphene-Based Electrochemical Paper-Based Analytical Device for a Portable Electrochemical Sensor for Xylazine Detection

A portable electrochemical device for xylazine detection is presented for the first time. An electrochemical paper-based analytical device (ePAD) was integrated with a smartphone. The fabrication of the ePAD involved wax printing, low-tack transfer tape, and cutting and screen-printing techniques. Graphene ink was coated on the substrate and modified with nanocoral-like polyaniline, providing an electron transfer medium with a larger effective surface area that promoted charge transfer. The conductive ink on the ePAD presented a thickness of 25.0 ± 0.9 μm for an effective surface area of 0.374 cm². This sensor was then tested directly on xylazine using differential pulse voltammetry. Two linear responses were obtained: from 0.2 to 5 μg mL^-1 and from 5 to 100 μg mL^-1. The detection limit was 0.06 μg mL^-1. Reproducibility was tested on 10 preparations. The relative standard deviation was less than 5%. The applicability of the sensor was evaluated with beverage samples spiked with trace xylazine. Recoveries ranged from 84 ± 4 to 105 ± 2%. The developed sensor demonstrated excellent accuracy in the detection of trace xylazine. It would be possible to develop the portable system to detect various illicit drugs to aid forensic investigations.

Xylazine poisoning: a systematic review

PURPOSE

Xylazine is an alpha-2-adrenergic agonist used for its sedative and analgesic properties in veterinary medicine. While not approved by the Food and Drug Administration for use in humans, anecdotal evidence suggests that exposures in humans is on the rise. We sought to systematically review and synthesize the evidence on xylazine exposure in humans focusing on the clinical presentation, management, and outcomes.

METHODS

We conducted a systematic review of the literature including PubMed, Embase, and Scopus from their inception to September 9, 2021. We searched abstracts from selected emergency medicine and toxicology conferences from 2011 through 2021. We included clinical reports of xylazine exposure in humans. We excluded animal studies, in vitro studies, laboratory studies, or articles in a language other than English. From each included article, we extracted subjective and objective data that focused on clinical presentation, management, and outcomes of patients exposed to xylazine.

RESULTS

We evaluated a total of 1409 records, rendering a final set of 17 articles and 2 abstracts meeting inclusion criteria. We identified a total of 98 patients amongst reports ranging from 1979 to 2020 and across nine countries. The most common types of xylazine exposures reported were unintentional exposure and intentional misuse/abuse. Common symptoms on presentation included hypotension, bradycardia, drowsiness, lethargy, while apnea with intubation and death were less frequently reported.

CONCLUSION

Human exposure to xylazine appears to be a rising concern within the prehospital and emergency medicine setting. Although a standardized treatment algorithm cannot be recommended at this time, further research is needed to improve the care of patients exposed to xylazine.

Xylazine spreads across the US: A growing component of the increasingly synthetic and polysubstance overdose crisis

BACKGROUND

Sharp exacerbations of the US overdose crisis are linked to polysubstance use of synthetic compounds. Xylazine is a veterinary tranquilizer, long noted in the street opioid supply of Puerto Rico, and more recently Philadelphia. Yet its national trends, geographic distribution, and health risks are poorly characterized.

METHODS

In this sequential mixed-methods study, xylazine was increasingly observed by ethnographers in Philadelphia among drug-sellers and people who inject drugs (PWID). Subsequently, we systematically searched for records describing xylazine-present overdose mortality across the US and assessed time trends and overlap with other drugs.

RESULTS

In 10 jurisdictions - representing all four US Census Regions - xylazine was increasingly present in overdose deaths, rising from 0.36% of deaths in 015m 6.7% in 2020. The highest xylazine prevalence data was observed in Philadelphia, (25.8% of deaths), followed by Maryland (19.3%) and Connecticut (10.2%). Illicitly-manufactured-fentanyls were present in 98.4% of xylazine-present-overdose-deaths - suggesting a strong ecological link - as well as cocaine (45.4%), benzodiazepines (28.4%), heroin (23.3%), and alcohol (19.7%). PWID in Philadelphia described xylazine as a sought-after adulterant that lengthens the short duration of fentanyl injections. They also linked it to increased risk of soft tissue infection and naloxone-resistant overdose.

CONCLUSIONS

Xylazine is increasingly present in overdose deaths, linked to the proliferation of illicitly-manufactured-fentanyls. Ethnographic accounts associate it with profound risks for PWID. Nevertheless, many jurisdictions do not routinely test for xylazine, and it is not comprehensively tracked nationally. Further efforts are needed to provide PWID with services that can help minimize additional risks associated with a shifting drug supply.

Xylazine Regulates the Release of Glycine and Aspartic Acid in Rat Brain

Introduction

Xylazine, a type of α₂-adrenoceptors, is a commonly used drug in veterinary medicine. Xylazine-induced changes in the content of amino acid neurotransmitters - glycine (Gly) and aspartic acid (Asp), in different brain regions and neurons were studied.

Material and Methods

Wistar rats were administered 50 mg/kg or 70 mg/kg of xylazine by intraperitoneal injection. In addition, in vitro experiments were conducted, in which neurons were treated with 15 μg/mL, 25 μg/mL, 35μg/mL, and 45 μg/mL of xylazine. Test methods were based on the enzyme-linked immunosorbent assays (ELISA).

Results

During anaesthesia, Asp levels in each brain area were significantly lower compared to the control group. Except for the cerebrum, levels of Gly in other brain areas were significantly increased during the anaesthesia period. In vitro, xylazine-related neuron secretion of Gly increased significantly compared to the control group at 60 min and 90 min. Moreover, xylazine caused a significant decrease in the levels of Asp secreted by neurons at 20 min, but gradually returned to the level of the control group.

Conclusion

The data showed that during anaesthesia the overall levels of Asp decreased and overall levels of Gly increased. In addition, the inhibitory effect of xylazine on Asp and the promotion of Gly were dose-dependent. Our data showed that different effects of xylazine on excitatory and inhibitory neurotransmitters provided a theoretical basis for the mechanism of xylazine activity in clinical anaesthesia.

Xylazine regulates the release of glycine and aspartic acid in rat brain

Introduction

Xylazine, a type of α2-adrenoceptors, is a commonly used drug in veterinary medicine. Xylazine-induced changes in the content of amino acid neurotransmitters – glycine (Gly) and aspartic acid (Asp), in different brain regions and neurons were studied.

Material and Methods

Wistar rats were administered 50 mg/kg or 70 mg/kg of xylazine by intraperitoneal injection. In addition, in vitro experiments were conducted, in which neurons were treated with 15 μg/mL, 25 μg/mL, 35μg/mL, and 45 μg/mL of xylazine. Test methods were based on the enzyme-linked immunosorbent assays (ELISA).

Results

During anaesthesia, Asp levels in each brain area were significantly lower compared to the control group. Except for the cerebrum, levels of Gly in other brain areas were significantly increased during the anaesthesia period. In vitro, xylazine-related neuron secretion of Gly increased significantly compared to the control group at 60 min and 90 min. Moreover, xylazine caused a significant decrease in the levels of Asp secreted by neurons at 20 min, but gradually returned to the level of the control group.

Conclusion

The data showed that during anaesthesia the overall levels of Asp decreased and overall levels of Gly increased. In addition, the inhibitory effect of xylazine on Asp and the promotion of Gly were dose-dependent. Our data showed that different effects of xylazine on excitatory and inhibitory neurotransmitters provided a theoretical basis for the mechanism of xylazine activity in clinical anaesthesia.