Production of human metabolites by gastrointestinal bacteria as a potential source of post-mortem alteration of antemortem drug/metabolite concentrations

Identification of 5-aminometonitazene and 5-acetamidometonitazene in a postmortem case: are nitro-nitazenes unstable?

In recent years, the use of 2-benzylbenzimidazole opioids ('nitazenes') has increased with them becoming one of the most prominent synthetic opioid subclasses of novel psychoactive substances. With the increased prevalence, there is also a concern of the dangers to public health with the use of nitazenes due to their high potency especially with polypharmacy. To aid in the detection of such compounds, it is important that forensic toxicology laboratories maintain up-to-date compound libraries for drug screening methods and that sensitive analytical instrumentation is available to detect the low blood/plasma concentrations of more potent drugs. This includes not only the compounds themselves but also potential metabolites and/or degradation products. Metonitazene is a 'nitro-nitazene' with a nitro group at position 5 of the benzimidazole ring. As a nitro-nitazene, there is a potential for bacterial degradation of metonitazene to 5-aminometonitazene, as occurs with nitro-benzodiazepines. In this study, we provide evidence from a postmortem (PM) case of degradation of metonitazene in unpreserved PM blood using liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ-MS), and putative identification of the degradation/metabolic products 5-aminometonitazene and 5-acetamidometonitazene by liquid chromatography-quadrupole time-of-flight mass spectrometry. The results from LC-QQQ-MS analysis indicated that there did not appear to be such degradation in preserved (fluoride/oxalate) blood. These results suggest that nitro-nitazenes may be subject to similar in vitro stability/degradation issues as nitro-benzodiazepines. These breakdown products should be added to instrument libraries to aid in the detection of the use of nitro-nitazenes, and nitro-nitazenes should be quantified in preserved blood samples where available.

Elucidating the potential role of microorganisms in postmortem biotransformation: a comparison of clonazolam and its metabolite in postmortem and DUID cases

Clonazolam is a designer triazolobenzodiazepine first synthesized in 1971 and is primarily used for its anxiolytic and sedative effects. It became a drug of misuse in 2012 and is known for its high potency and long duration of effect. Previous studies of nitrobenzodiazepines, such as nitrazepam, clonazepam, and flunitrazepam, as well as their metabolites, have demonstrated that bacterial species native to the gastrointestinal tract and active during postmortem (PM) decomposition are capable of affecting positivity and compound-to-metabolite ratios. Further studies have not been performed with clonazolam; however, it possesses the nitro functional group necessary for this biotransformation. To understand whether clonazolam may be similarly affected, PM cases (n = 288) and driving under the influence of drugs (DUID, n = 54) cases, positive for 8-aminoclonazolam reported by NMS Laboratories from 2020 to 2023, were selected for inclusion in this study. Concentrations of clonazolam and 8-aminoclonazolam were evaluated, and concurrent identification of parent drugs and their metabolites occurred less frequently in PM cases (n = 1, 0.30% of cases) than in DUID cases (n = 21, 38% of cases). The clonazolam concentration in one PM case was 13 ng/mL. In DUID cases, the median clonazolam concentration was 4.0 ng/mL and ranged from 2.0 to 10 ng/mL. 8-Aminoclonazolam had median concentrations of 13 and 19 ng/mL, with ranges 2.0-580 and 2.8-59 ng/mL for PM and DUID cases, respectively. Due to the ever-changing landscape of the designer benzodiazepine market, in vitro studies of PM microbial biotransformation of clonazolam are unavailable. The data reported herein provide valuable information in the absence of such studies and represent an alternative method of investigating this phenomenon as a potential cause of parent nitrobenzodiazepine to metabolite conversion.

The role of microorganisms in the biotransformation of psychoactive substances and its forensic relevance: a critical interdisciplinary review

Microorganisms are widespread on the planet being able to adapt, persist, and grow in diverse environments, either rich in nutrient sources or under harsh conditions. The comprehension of the interaction between microorganisms and drugs is relevant for forensic toxicology and forensic chemistry, elucidating potential pathways of microbial metabolism and their implications. Considering the described scenario, this paper aims to provide a comprehensive and critical review of the state of the art of interactions amongst microorganisms and common drugs of abuse. Additionally, other drugs of forensic interest are briefly discussed. This paper outlines the importance of this area of investigation, covering the intersections between forensic microbiology, forensic chemistry, and forensic toxicology applied to drugs of abuse, and it also highlights research potentialities.

Key points

Microorganisms are widespread on the planet and grow in a myriad of environments.Microorganisms can often be found in matrices of forensic interest.Drugs can be metabolized or produced (e.g. ethanol) by microorganisms.

Investigations into the stability of 17 psychoactive drugs in a "simulated postmortem blood" model

In the postmortem environment some drugs and metabolites may degrade due to microbial activity, even forming degradation products that are not produced in humans. Consequently, under- or over-estimation of perimortem drug concentrations or even false negatives are possible when analyzing postmortem specimens. Therefore, understanding whether medications may be susceptible to microbial degradation is critical in order to ensure that reliable detection and quantitation of drugs and their degradation products is achieved in toxicology screening methods. In this study, a "simulated postmortem blood" model constructed of antemortem human whole blood inoculated with a broad population of human fecal microorganisms was used to investigate the stability of 17 antidepressant and antipsychotic drugs. Microbial communities present in the experiments were determined to be relevant to postmortem blood microorganisms by 16S rRNA sequencing analyses. After 7 days of exposure to the community at 37 °C, drug stability was evaluated using liquid chromatography coupled with diode array detection (LC-DAD) and with quadrupole time of flight mass spectrometry (LC-QTOF-MS). Most of the investigated drugs were found to be stable in inoculated samples and non-inoculated controls. However, the 1,2-benzisothiazole antipsychotics, ziprasidone and lurasidone, were found to degrade at a rate comparable to the known labile control, risperidone. In longer experiments (seven to twelve months), where specimens were stored at -20 °C, 4 °C, and ambient temperature, N-dealkylation degradation products were detected for many of the drugs, with greater formation in specimens stored at -20 °C than at 4 °C.

Identification of Unique 4-Methylmethcathinone (4-MMC) Degradation Markers in Putrefied Matrices†

Drug degradation as a consequence of putrefactive bacterial activity is a well-known factor that affects the identification and quantitation of certain substances of forensic interest. Current knowledge on putrefaction-mediated degradation of drugs is, however, significantly lacking. This study aimed to investigate the degradation of 4-methylmethcathinone (4-MMC or mephedrone) and to detect its degradation products in putrefied biological matrices containing 4-MMC. The bacteria species Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris were grown in brain-heart infusion broth, spiked with 4-MMC and incubated at 37°C for 24 h. Postmortem human blood and fresh porcine liver macerate were also left to putrefy in sample tubes at room temperature for 1 week. Structural elucidation was based on modern spectroscopic analyses including the use of high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy. All four putrefactive bacteria were capable of degrading 4-MMC extensively under the experimental conditions explored. Of particular interest was the discovery of a novel degradation product common to all four bacterial species, which was assigned as 2-hydroxy-1-(4-methylphenyl)propan-1-one (HMP) based on the spectroscopic data. This degradation product was detectable in both postmortem human blood and porcine liver samples. The stability of the identified degradation products, especially HMP, should be further investigated to assess their validity of serving as marker analytes for monitoring 4-MMC in postmortem toxicology.

Present and foreseeable future of metabolomics in forensic analysis

The revulsive publications during the last years on the precariousness of forensic sciences worldwide have promoted the move of major steps towards improvement of this science. One of the steps (viz. a higher involvement of metabolomics in the new era of forensic analysis) deserves to be discussed under different angles. Thus, the characteristics of metabolomics that make it a useful tool in forensic analysis, the aspects in which this omics is so far implicit, but not mentioned in forensic analyses, and how typical forensic parameters such as the post-mortem interval or fingerprints take benefits from metabolomics are critically discussed in this review. The way in which the metabolomics-forensic binomial succeeds when either conventional or less frequent samples are used is highlighted here. Finally, the pillars that should support future developments involving metabolomics and forensic analysis, and the research required for a fruitful in-depth involvement of metabolomics in forensic analysis are critically discussed.