Broad evidence of xylazine in the UK illicit drug market beyond heroin supplies: Triangulating from toxicology, drug-testing and law enforcement

BACKGROUND AND AIMS

Xylazine is a non-opioid sedative which has spread rapidly throughout the US illicit drug supply. This study aimed to describe the spread of xylazine throughout the UK illicit drug supply.

METHODS

Xylazine detections in human biological samples were collated from toxicology laboratories operating in the United Kingdom with the date, location, case type, xylazine concentration and co-detected drugs (with quantifications where performed) detailed, where permitted, by the corresponding coroner. Drug-testing cases positive for xylazine were collated from the Welsh Emerging Drugs and Identification of Novel Substances (WEDINOS) drug-testing postal service with the date, location, purchase intent and co-detected drugs detailed. Drug seizures made by UK law enforcement were communicated by the Office for Health Improvement and Disparities with the date and location detailed.

RESULTS

By the end of August 2023, xylazine was detected in 35 cases from throughout toxicology, drug-testing and drug seizure sources covering England, Scotland and Wales. There were no cases reported from Northern Ireland. Xylazine was detected in biological samples from 16 people. In most cases where full toxicology results were provided, xylazine was detected with heroin and/or a strong opioid (n = nine of 11), but this polydrug use pattern was not evident in all cases (n = two of 11), suggesting a wider circulation of xylazine in the UK illicit drug market beyond heroin supplies. Evidence from WEDINOS supports this claim, as all 14 drug samples (100%) submitted from across the UK contained xylazine; however, in none of these cases was heroin the purchase intent but rather counterfeit prescription medication tablets (n = 11 of 14), tetrahydrocannabinol (THC) vapes (n = two of 14) or white powder (n = one of 14). Additional evidence for the spread of illicit xylazine comes from five drug seizures made by law enforcement.

CONCLUSIONS

Xylazine has penetrated the UK illicit drug market and is not limited to heroin supplies.

Evaluating the regulatory function of non-coding autism-associated single nucleotide polymorphisms on gene expression in human brain tissue

Common variants account for most of the estimated heritability associated with autism spectrum disorder (autism). Although several replicable single nucleotide polymorphisms (SNPs) for the condition have been detected using genome-wide association study (GWAS) methodologies, their pathophysiological relevance remains elusive. Examining this is complicated, however, as all detected loci are situated within non-coding regions of the genome. It is therefore likely that they possess roles of regulatory function as opposed to directly affecting gene coding sequences. To bridge the gap between SNP discovery and mechanistic insight, we applied a comprehensive bioinformatic pipeline to functionally annotate autism-associated polymorphisms and their non-coding linkage disequilibrium (i.e., non-randomly associated) partners. We identified 82 DNA variants of probable regulatory function that may contribute to autism pathogenesis. To validate these predictions, we measured the impact of 11 high-confidence candidates and their GWAS linkage disequilibrium partners on gene expression in human brain tissue from Autistic and non-Autistic donors. Although a small number of the surveyed variants exhibited measurable influence on gene expression as determined via quantitative polymerase chain reaction, these did not survive correction for multiple comparisons. Additionally, no significant genotype-by-diagnosis effects were observed for any of the SNP-gene associations. We contend that this may reflect an inability to effectively capture the modest, neurodevelopmental-specific impact of individual variants on biological dysregulation in available post-mortem tissue samples, as well as limitations in the existing autism GWAS data.

Evaluation of public and animal health risks in case of a delayed post-mortem inspection in ungulates

The potential effects of a 24 or 72-h delay in post-mortem inspection (PMI) of ungulates on public health and monitoring of animal health and welfare was evaluated. The assessment used a survey of meat inspectors, expert opinion, literature search and a stochastic model for Salmonella detection sensitivity. Disease detection sensitivity at a delayed PMI is expected to reduce detection sensitivity to a variable extent, depending on the hazard and on the signs/lesions and organs involved. No reduction is expected for Trichinella detection in meat from susceptible animal species and any decrease in detection of transmissible spongiform encephalopathies (TSEs) will not exceed the current tolerance for fallen stock. A 24-h delay in PMI could result in a small reduction in sensitivity of detection for tuberculosis, echinococcosis and cysticercosis. A greater reduction is expected for the detection of pyaemia and Rift valley fever. For the detection of Salmonella, the median model estimates are a reduction of sensitivity of 66.5% (90% probability interval (PI) 0.08-99.75%) after 24-h delay and 94% (90% PI 0.83-100%) after 72-h delay of PMI. Laboratory testing for tuberculosis following a sampling delay of 24-72 h could result in no, or a moderate, decrease in detection depending on the method of confirmation used (PCR, culture, histopathology). For chemical contaminants, a delay in meat inspection of 24 or 72 h is expected to have no impact on the effectiveness of detection of persistent organic pollutants and metals. However, for certain pharmacologically active substances, there will be a reduced effectiveness to detect some of these substances due to potential degradation in the available matrices (tissues and organs) and the non-availability of specific preferred matrices of choice.