Analytical methods for the determination of xylazine in pharmaceutical, clinical and forensic matrices – A review

Xylazine, a non-opioid veterinary anaesthetic tranquillizer that is not licensed for human use, has been linked to an increase in overdose fatalities worldwide. The study delves into the forensic aspects of xylazine usage, emphasizing on chemical, clinical and toxicological analyses of drug seizures, bodily fluids and tissues. It advocates for validated analytical methods for determining xylazine. This study provides supporting material to pave the path for the usage and development of relevant and verified alternative screening and confirmation methods for laboratories. Google Scholar, Scopus, Science Direct and PubMed were searched for relevant articles and case reports in relation to xylazine misuse and established analytical methods for forensic investigation until April 2023. A total of 79 articles were evaluated, and 40 publications met the inclusion criteria. The most prevalent xylazine exposures recorded were incidental and intentional misuse/abuse. Common symptoms upon presentation were hypotension, bradycardia, drowsiness and lethargy, although mortality was less prevalent. Solid-phase extraction and liquid–liquid extraction are two extensively used sample preparation techniques. These techniques are used to extract desired analytes from complex matrices. Several analytical techniques have been stated, including GC–MS, LC–MS/MS, HPLC–DAD and others. The analytical procedures used are determined by the matrices involved, the amount of xylazine present, interfering compounds, the degree of precision required and the laboratory infrastructure. In the present context, the LC–MS/MS methods are preferred as the gold standard. In the near future, many analytical techniques such as capillary electrophoresis, PSI-MS, immuno-analytical techniques and SERRS may show significant potential.