Xylazine, a Veterinary Tranquilizer, Detected in 42 Accidental Fentanyl Intoxication Deaths

ABSTRACT

Xylazine is an emerging adulterant with fentanyl in fatal drug intoxications, which has public health, safety, and criminal investigative implications. Xylazine is a nonnarcotic sedative used for analgesia and muscle relaxation exclusively in veterinary medicine. Its chemical structure is similar to clonidine and acts as a central α-2 agonist which may cause bradycardia and transient hypertension followed by hypotension. We report the detection of xylazine in 42 deaths in Connecticut from March to August 2019. Xylazine combined with an opioid or stimulant may affect the toxicity of these drugs. Detection of xylazine may help the forensic pathologist distinguish illicit from prescribed fentanyl, and law enforcement agents track the illicit drugs to a specific drug supplier. Because of its lack of response to naloxone, emergency medicine physicians need to be aware of its potential presence as it may affect therapy.

Pharmacokinetics of ketamine and xylazine in young and old Sprague-Dawley rats

To compare the pharmacokinetics of coadministered intraperitoneal ketamine and xylazine in young (8 to 10 wk; n = 6) and old rats (2 to 2.4 y; n = 6), blood samples obtained at 15 and 30 min and 1, 2, and 4 h after drug administration were analyzed by HPLC-tandem mass spectrometry. In both groups, the withdrawal reflex was absent during anesthesia and was present at 1.1 (± 0.2) and 2.6 (± 0.7) h after drug administration in young and old rats, respectively, with the first voluntary movement at 1.5 ± 0.2 and 4.9 ± 1.0 h. Drug availability of ketamine and xylazine was 6.0 and 6.7 times greater, respectively, in old than young rats. The rate constant of elimination of both drugs was greatly decreased and the elimination half-life was significantly greater in old compared with young rats. In conclusion, age and associated factors affect the availability of ketamine and xylazine when coadministered to attain clinical anesthesia, changing the pharmacokinetics of these drugs and prolonging anesthesia duration and recovery times with aging. Compared with their young counterparts, aged rats required much higher doses to attain a similar level of anesthesia. Finally, the long half-life of both ketamine and xylazine, when coadministered to old rats, may be a factor in research protocols because residual plasma concentrations could still be present for as long as 3 and 5 d, respectively, after administration.

Solid-Phase Extraction and Gas Chromatographic-Mass Spectrometric Determination of the Veterinary Drug Xylazine in Human Blood

This paper presents a method for the determination of xylazine in whole blood using solid-phase extraction and gas chromatography-mass spectrometry. This technique required only 0.5 mL of sample, and protriptyline was used as internal standard (IS). Limits of detection and quantitation (LOQ) were 2 and 10 ng/mL, respectively. The method was found to be linear between the LOQ and 3.50 microg/mL, with correlation coefficients higher than 0.9922. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The analyte was stable in the matrix for at least 18 h at room temperature and for at least three freeze/thaw cycles. Mean recovery, calculated at three concentration levels, was 87%. To the best of our knowledge, this is the first time that solid-phase extraction is used as sample preparation technique for the determination of this compound in biological media. Because of its simplicity and speed when compared to other extraction techniques, the herein described method can be successfully applied in the diagnosis of intoxications by xylazine.

Determination of Acepromazine, Ketamine, Medetomidine, and Xylazine in Serum: Multi-Residue Screening by Liquid Chromatography-Mass Spectrometry

A large variety of drugs are administered to large and small animals by veterinary clinicians for sedation, anesthesia, muscle relaxation, and analgesia. The present paper reports a simple and rapid multi-residue detection and quantitation method for four chemically different drugs: medetomidine, xylazine, ketamine, and acepromazine. Chromatographic separation was carried out on a liquid chromatography-mass spectrometry instrument with a C18-reversed-phase column. Fragmentation patterns were determined with atmospheric pressure chemical ionization mass spectrometry set to operate in a positive selective ion monitoring mode. The method was determined to be linear over the range of concentrations tested (2.0-100.0 ng/mL). Accuracy, precision, and specificity were evaluated and the method was determined to be applicable to detection of medetomidine, xylazine, ketamine, and acepromazine in serum samples of multiple animal species (canine, equine, and bovine). Matrix limits of quantitation were determined to be 5.0 ng/mL for all four analytes, and recoveries ranged between 82.0 and 118%, with a 3.0-18.3% relative standard deviation.

Simultaneous determination of ketamine and xylazine in canine plasma by liquid chromatography with ultraviolet absorbance detection

An isocratic reversed-phase high-performance liquid chromatographic method for the simultaneous determination of ketamine and xylazine in canine plasma is described. Plasma samples (500 microl) are cleaned up via liquid-liquid extraction. The analytes and the internal standard clonidine are separated on a cyano (CN) column using a mobile phase containing acetonitrile-0.005 M phosphate buffer adjusted to pH 5.5 (3:2) at a detection wavelength of 215 nm. The method was validated according to specificity, sensitivity, accuracy and reproducibility and was used to determine the plasma concentrations of both compounds in dogs after intramuscular injection.

A reported case involving impaired driving following self-administration of xylazine

A case of suspected drug-impaired driving involving self-administration of xylazine (Xyla-Ject), a veterinary tranquilizing agent, and paroxetine is presented. Qualitative and quantitative analysis of xylazine and paroxetine were performed by gas chromatography with a flame-ionization detector (GC-FID) and gas chromatography/mass spectrometry (GC/MS). Whole blood xylazine and paroxetine concentrations were 0.57 and 0.02 microg/ml, respectively.

Tissue distribution of xylazine in a suicide by hanging

Xylazine (Rompun, Sedazine, AnaSed) is currently the most commonly used sedative-analgesic in veterinary medicine. There are nine published cases of xylazine's involvement in human drug-related deaths and impairment. However, blood concentrations were reported in only four of these cases. Three of these nine cases were fatalities involving xylazine, two of which involved xylazine alone but did not report blood concentrations because of extensive decomposition of the bodies. This report documents a case in which xylazine alone was identified in a suicide by hanging. The following xylazine concentrations were found: 2.3 mg/L in heart blood; 2.9 mg/L in peripheral (subclavian) blood; 6.3 mg/L in bile; 0.01 mg/L in urine; 6.1 mg/kg in liver; and 7.8 mg/kg in kidney.

Pharmacokinetics of xylazine, 2,6-dimethylaniline, and tolazoline in tissues from yearling cattle and milk from mature dairy cows after sedation with xylazine hydrochloride and reversal with tolazoline hydrochloride

Xylazine hydrochloride was administered i.m. at 0.35 mg/kg to 13 steers and 10 lactating dairy cows at Time 0. Ten minutes later, tolazoline hydrochloride was given i.v. at 4 mg/kg. Tissue and milk samples were analyzed using gas chromatography with nitrogen and phosphorous detection to determine concentrations of xylazine, 2,6-dimethylaniline (a toxic metabolite of xylazine), and tolazoline (at various intervals). Concentrations of xylazine and 2,6- dimethylaniline were below the limit of quantitation (10 microg/kg) by 72 hours in tissues and 12 hours in milk. The concentration of tolazoline was below 10 microg/kg by 96 hours in tissues and 48 hours in milk. Based on the results of these residue studies submitted by the sponsoring agency to the Ministry of Agriculture and Forestry in New Zealand, withholding periods for both xylazine hydrochloride and tolazoline hydrochloride injection were established.

Severe intoxication with the veterinary tranquilizer xylazine in humans

Xylazine (Rompun, Proxylaz) is a veterinary tranquilizing agent. A case of self-injection of 1.5 g xylazine by a 27-year-old farmer is reported. He subsequently became comatose, hypotensive, bradycardic, and mildly glycemic. An intensive supportive therapy including intubation and ventilation was required. The patient made a full recovery over the next 30 h. The largest concentrations measured were 4.6 mg/L in plasma, 446 mg/L in gastric fluid, and 194 mg/L in urine. The calculated plasma half-life was 4.9 h. Kinetic data correlated with clinical symptoms. Qualitative and quantitative analyses of xylazine were done by thin-layer chromatography, gas chromatography-mass spectrometry, and high-performance liquid chromatography. These methods allow the detection of small amounts substance in stomach, plasma, and urine. Liquid-liquid extraction was used for the isolation of drug. The sensitvity is high, and with these methods, a rapid analysis is possible. Xylazine intoxications in humans are rare. We describe the management of acute poisoning and present a review of xylazine toxicity in humans.

Toxicity and blood concentrations of xylazine and its metabolite, 2,6-dimethylaniline, in rats after single or continuous oral administrations

To cast light on whether the carcinogenic risk of 2,6-dimethylaniline (DMA), a metabolite of xylazine, may increase by ingestion of edible tissues from domestic animals treated with xylazine, the following studies of xylazine and DMA were performed. In Experiment I, male F344 rats received a single oral administration of 150 mg/kg of xylazine hydrochloride. Rats showed symptoms suggesting loss of sensation and pain immediately after the treatment. These signs had disappeared after 3 hr, but the animals died of hydrothorax and pulmonary edema by 9 hr. The plasma concentration of xylazine was 2.88 +/- 0.95 micrograms/ml at 15 min, and then decreased to 0.10 +/- 0.01 microgram/ml at 6 hr. The plasma level of DMA remained at 0.03 to 0.04 microgram/ml during the measurement period. In Experiment II, male F344 rats were fed a diet containing 1000 ppm of xylazine hydrochloride, regarded as the maximum tolerated dose, for 4 weeks. No clear clinical signs were evident and the plasma levels of xylazine and DMA were at the detection limit (0.02 microgram/ml) or less, although follicular cell hypertrophy of the thyroid was observed in all the treated animals. In Experiment III, male F344 rats were fed a diet containing 3000 ppm or 300 ppm of DMA for 4 weeks. Histological changes, such as atrophy of Bowman's gland and irregular arrangement of olfactory epithelial cells, were only observed in the olfactory epithelium of the 3000 ppm group. The plasma levels of DMA were 0.20 to 0.36 microgram/ml in the 3000 ppm group, but under the detection limit in the 300 ppm group. These results suggest that the probability of nasal carcinogenic effects of DNA on consumers via ingestion of edible tissues from food-producing animals treated with xylazine is extremely low, since DMA levels in the blood of rats subjected to continuous administration of high doses of xylazine remained under the detection limit.

The effects of medetomidine and xylazine on gastrointestinal motility and gastrin release in the dog

The effect of medetomidine, a potent and highly selective alpha2-adrenoceptor agonist, on the motility of the gastric antrum, duodenum, mid-jejunum and ileum was investigated in ten dogs. Its effect on the release of gastrin was also determined. Administration of medetomidine intramuscularly (i.m.) at a dose of 40 microg/kg inhibited the motility of the gastric antrum, duodenum, mid-jejunum and ileum significantly, in comparison to administration of xylazine intramuscularly at a dose of 2.0 mg/kg. The release of gastrin was also significantly decreased in dogs receiving medetomidine. It was found to inhibit the motility in the gastric antrum and duodenum longer than in the mid-jejunum and ileum, presumably by acting specifically on alpha2-adrenoceptors, likely at the peripheral level. Medetomidine also inhibited the gastric contraction associated with gastrin secretion.

[Evaluation of the antinociceptive effect of xylazine after epidural administration in dogs under general anesthesia with isoflurane]

Seven dogs anaesthetized with isoflurane in oxygen (1.9 Vol.-% ET) were examined before and after lumbosacral injection of xylazine (0.25 mg/kg) into the epidural space. Over a 240 minute period the dogs were first stimulated in a visceral manner (extension of the colon descendens by a balloon-catheter) every 15 minutes. In a second part, the dogs were stimulated somatically by pressure to the interdigital skin of a hindlimb. Heart rate and mean arterial pressure were used to determine the analgesic properties of epidurally injected xylazine. Furthermore, plasma xylazine concentration was controlled in both series. Before epidural anaesthesia, heart rate and mean arterial pressure increased during stimulation significantly in both groups. After epidural injection of xylazine, hemodynamic reactions were distinctly diminished, in the somatically stimulated group more than in the viscerally stimulated group. Up to 30 minutes after epidural injection, plasma xylazine concentrations of about 100 ng/ml were found in both groups. Up to 60 minutes after epidural injection, plasma xylazine concentrations of more than 60 ng/ml still were found. From the 120th minute on, xylazine concentration decreased below 30 ng/ml. From these results, it can be concluded that there is a well-suited analgesic effect of epidurally applicated xylazine for approximately 240 minutes.

[Pharmacokinetics and effects of xylazine (Rompun) in dogs]

Six beagle dogs were treated with xylazine hydrochloride (1 mg/kg i.m.). The plasma xylazine concentration was measured by HPLC. Additionally, clinical effects were registered (cardiac rate, respiratory activity, electrocardiogram, body temperature, motoric activity, attention, analgesia). Maximum plasma concentrations were measured after 15 minutes (476 ng/ml). The plasma half-life was 24 minutes. Sedation was registered over one hour (xylazine concentration of more than 150 ng/ml). Within the first 30 minutes after treatment (xylazine concentration of more than 300 ng/ml), a low-grade analgesia was observed. In contrast, cardiac and respiratoric depression and also significantly diminished body temperature were registered over 2 to 3 hours.

Radioreceptor assay for determination of xylazine and medetomidine in sheep plasma

A radioreceptor assay technique is described for the measurement of xylazine and medetomidine in sheep plasma. The assay was based on the displacement of tritiated clonidine from a2-adrenoceptors in a rat brain homogenate by xylazine or medetomidine extracted from plasma. Plasma samples from sheep which had been given xylazine and medetomidine were treated with alumina to remove endogenous catecholamines which would otherwise have bound to alpha 2-adrenoceptors and interfered with the assay. The drugs were then extracted using chloroform, reconstituted in buffer and used to displace [3H]clonidine. The concentration of alpha 2-agonist was calculated by reference to standard curves. The method had a detection limit of 2.5 ng/mL for xylazine and 0.24 ng/mL for medetomidine. The assay could also be used to detect metabolites capable of binding to alpha 2-receptors.

Chemical capture of free-ranging cattle: immobilization with xylazine or medetomidine, and reversal with atipamezole

Twenty-nine free-ranging Norwegian cattle were captured with xylazine (n = 20) or medetomidine (n = 9) using a tranquilizing gun, and the time from darting to recumbency (induction time) was recorded. Twenty-eight animals were given atipamezole IV 15-100 min after darting, and the effects of the antagonist were evaluated. Blood samples (n = 19) for haematology and serum chemistry were collected within 10 min after immobilization was induced. Xylazine (0.55 +/- 0.18 mg/kg; mean +/- SD; n = 18) or medetomidine-HCl (0.039 +/- 0.10 mg/kg; n = 8) induced complete immobilization after a single darting with sternal or lateral recumbency, the induction times being 9.6 +/- 3.8 and 12.0 +/- 6.8 min, respectively. No difference in the clinical effects of the two drugs was observed. Rapid reversal was achieved with 0.057 +/- 0.017 and 0.077 +/- 0.019 mg/kg of atipamezole-HCl in xylazine- and medetomidine-treated animals, respectively. All the animals stood within 2 min after IV administration of the antagonist. Seven animals showed signs of excitement shortly after reversal, but these side-effects were of brief duration. Heavy resedation with relapse into recumbency was seen 3-4 h after reversal in two cows captured with xylazine, while moderate resedation was observed in two medetomidine-treated animals 2 h after reversal. Except for the plasma glucose concentration, which was elevated in both xylazine- and medetomidine-treated animals, the mean values of the haematological and plasma chemical parameters were within the reference ranges established for Norwegian cattle.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics of xylazine hydrochloride: an interspecific study

The pharmacokinetic disposition of xylazine hydrochloride is described after both intravenous and intramuscular injection of a single dose, in four domestic species: horse, cattle, sheep and dog, by an original high performance liquid chromatographic technique. Remarkably small interspecific differences are reported. After intravenous administration, systemic half-life (t1/2 beta) ranged between 22 min (sheep) and 50 min (horse) while the distribution phase is transient with half-life (t1/2 alpha) ranging from 1.2 min (cattle) to 5.9 min (horse). The peak level of drug concentration in the plasma is reached after 12-14 min in all the species studied following intramuscular administration. Xylazine bioavailability, as measured by the ratios of the areas under the intravenous and intramuscular plasma concentration versus time curves, ranged from 52% to 90% in dog, 17% to 73% in sheep and 40% to 48% in horse. The low dosage in cattle did not permit calculation. Kinetic data are correlated with clinical data and the origins of interspecific differences are discussed.