Recent trends in drugs of abuse metabolism studies for mass spectrometry–based analytical screening procedures

Abstract

The still increasing number of drugs of abuse, particularly the so-called new psychoactive substances (NPS), poses an analytical challenge for clinical and forensic toxicologists but also for doping control. NPS usually belong to various classes such as synthetic cannabinoids, phenethylamines, opioids, or benzodiazepines. Like other xenobiotics, NPS undergo absorption, distribution, metabolism, and excretion processes after consumption, but only very limited data concerning their toxicokinetics and safety properties is available once they appear on the market. The inclusion of metabolites in mass spectral libraries is often crucial for the detection of NPS especially in urine screening approaches. Authentic human samples may represent the gold standard for identification of metabolites but are often not available and clinical studies cannot be performed due to ethical concerns. However, numerous alternative in vitro and in vivo models are available. This trends article will give an overview on selected models, discuss current studies, and highlight recent developments.

Reviewing toxicokinetics with a focus on metabolism of new psychoactive substances in the zebrafish (larvae) model

“…Wagmann et al also found the zebrafish and zebrafish larvae to be a promising and emerging topic in metabolism studies of NPS but also concluded that establishing and maintaining a zebrafish culture platform is expensive and experienced personnel are required (Wagmann et al, 2021). However, no matter which model—adult zebrafish or larvae—will be used, there is still a need for standardization of the model and to extent the knowledge of similarity with human metabolism (de Souza Anselmo et al, 2018).…”

Metabolism of third generation synthetic cannabinoids using zebrafish larvae

“…While in silico models exist to assist with the prediction of these properties, 9,10 in vitro experiments 11,12 and more so in vivo studies are imperative to fully confirm the behavior of a new substance. 13 Several alternatives to in vitro models have been proposed, such as human liver microsomes (HLM), human liver S9 fraction (HLS9), primarily cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) isozymes, and primary human hepatocytes (PHH). 14 On the other hand, traditional in vivo tools to study metabolism of NPS include rats, 15 the most commonly used mammalian model, chimeric mice with a humanized liver, 16 pig, 17 and zebrafish and zebrafish larvae.…”

“…Apart from adult zebrafish, zebrafish larvae have been used in metabolism studies, because larvae provide the main benefits of adult individuals but are not considered as animals until 5-day postfertilization (dpf) according to the European Directive 2010/63/EU, and thus, experiments with zebrafish larvae do not require an ethical approval in the EU if they are completed within 5 days after fertilization. 13 Other advantages of zebrafish and zebrafish larvae models are related to the high degree ofphysiological and genetic homology to humans. 20 According to Howe et al, zebrafish genome, fully sequenced, shows orthologues corresponding to $82% of disease-related genes in humans.…”

“…In this sense, metabolism and toxicity of many synthetic cannabinoids, especially those belonging to the third generation, are poorly studied and remain largely unknown. While in silico models exist to assist with the prediction of these properties, 9,10 in vitro experiments 11,12 and more so in vivo studies are imperative to fully confirm the behavior of a new substance 13 . Several alternatives to in vitro models have been proposed, such as human liver microsomes (HLM), human liver S9 fraction (HLS9), primarily cytochrome P450 (CYP) and UDP‐glucuronosyltransferase (UGT) isozymes, and primary human hepatocytes (PHH) 14 .…”

“…Zebrafish model provides several advantages over other existing models such as small size, easy maintenance, low cost, and high reproductive rate. Apart from adult zebrafish, zebrafish larvae have been used in metabolism studies, because larvae provide the main benefits of adult individuals but are not considered as animals until 5‐day postfertilization (dpf) according to the European Directive 2010/63/EU, and thus, experiments with zebrafish larvae do not require an ethical approval in the EU if they are completed within 5 days after fertilization 13 . Other advantages of zebrafish and zebrafish larvae models are related to the high degree ofphysiological and genetic homology to humans 20 .…”