Bioanalytical Methods for New Psychoactive Substances

Current state-of-the-art approaches for mass spectrometry in clinical toxicology: an overview

INTRODUCTION

Hyphenated mass spectrometry (MS) has evolved into a very powerful analytical technique of high sensitivity and specificity. It is used to analyze a very wide spectrum of analytes in classical and alternative matrices. The presented paper will provide an overview of the current state-of-the-art of hyphenated MS applications in clinical toxicology primarily based on review articles indexed in PubMed (1990 to April 2023).

AREAS COVERED

A general overview of matrices, sample preparation, analytical systems, detection modes, and validation and quality control is given. Moreover, selected applications are discussed.

EXPERT OPINION

A more widespread use of hyphenated MS techniques, especially in systematic toxicological analysis and drugs of abuse testing, would help overcome limitations of immunoassay-based screening strategies. This is currently hampered by high instrument cost, qualification requirements for personnel, and less favorable turnaround times, which could be overcome by more user-friendly, ideally fully automated MS instruments. This would help making hyphenated MS-based analysis available in more laboratories and expanding analysis to a large number of organic drugs, poisons, and/or metabolites. Even the most recent novel psychoactive substances (NPS) could be presumptively identified by high-resolution MS methods, their likely presence be communicated to treating physicians, and be confirmed later on.

In vitro metabolic fate of the synthetic cannabinoid receptor agonists (quinolin-8-yl 4-methyl-3-(morpholine-4-sulfonyl)benzoate [QMMSB]) and (quinolin-8-yl 4-methyl-3-((propan-2-yl)sulfamoyl)benzoate [QMiPSB]) including isozyme mapping and carboxylesterases activity testing

The synthetic cannabinoid receptor agonists (SCRAs) (quinolin-8-yl 4-methyl-3-(morpholine-4-sulfonyl)benzoate [QMMSB]) and (quinolin-8-yl 4-methyl-3-((propan-2-yl)sulfamoyl)benzoate [QMiPSB], also known as SGT-46) are based on the structure of quinolin-8-yl 4-methyl-3-(piperidine-1-sulfonyl)benzoate (QMPSB) that has been identified on seized plant material in 2011. In clinical toxicology, knowledge of the metabolic fate is important for their identification in biosamples. Therefore, the aim of this study was the identification of in vitro Phase I and II metabolites of QMMSB and QMiPSB in pooled human liver S9 fraction (pHLS9) incubations for use as screening targets. In addition, the involvement of human monooxygenases and human carboxylesterases (hCES) was examined. Analyses were performed by liquid chromatography coupled with high-resolution tandem mass spectrometry. Ester hydrolysis was found to be an important step in the Phase I metabolism of both SCRAs, with the carboxylic acid product being found only in negative ionization mode. Monohydroxy and N-dealkyl metabolites of the ester hydrolysis products were detected as well as glucuronides. CYP2C8, CYP2C9, CYP3A4, and CYP3A5 were involved in hydroxylation. Whereas enzymatic ester hydrolysis of QMiPSB was mainly catalyzed by hCES1 isoforms, nonenzymatic ester hydrolysis was also observed. The results suggest that ester hydrolysis products of QMMSB and QMiPSB and their glucuronides are suitable targets for toxicological screenings. The additional use of the negative ionization mode is recommended to increase detectability of analytes. Different cytochrome P450 (CYP) isozymes were involved in the metabolism; thus, the probability of drug-drug interactions due to CYP inhibition can be assessed as low.

In Vitro Metabolic Fate of the Synthetic Cannabinoid Receptor Agonists 2F-QMPSB and SGT-233 Including Isozyme Mapping and Carboxylesterases Activity Testing

Quinolin-8-yl 3-(4,4-difluoropiperidine-1-sulfonyl)-4-methylbenzoate (2F-QMPSB) and 3-(4,4-difluoropiperidine-1-sulfonyl)-4-methyl-N-(2-phenylpropan-2-yl)benzamide (SGT-233) belong to a new group of synthetic cannabinoid receptor agonists containing a sulfamoyl benzoate or sulfamoyl benzamide core structure. 2F-QMPSB was identified in herbal material seized in Europe in 2018. The aims of this study were the identification of in vitro Phase I and II metabolites of 2F-QMPSB and SGT-233 to find analytical targets for toxicological screenings. Furthermore, the contribution of different monooxygenases and human carboxylesterases to Phase I metabolism was investigated. Liquid chromatography coupled to high-resolution tandem mass spectrometry was used for analysis. Ester hydrolysis was found to be an important step in the metabolism of 2F-QMPSB, which was catalyzed mainly by human carboxylesterases (hCES)1 isoforms. Additionally, nonenzymatic ester hydrolysis was observed in case of 2F-QMPSB. Notably, the carboxylic acid product derived from ester hydrolysis and metabolites thereof were only detectable in negative ionization mode. In case of SGT-233, mono- and dihydroxy metabolites were identified, as well as glucuronides. The cytochrome P450 (CYP) isozymes CYP2C8, CYP2C9, CYP2C19, CYP3A4 and CYP3A5 were found to be involved in the hydroxylation of both compounds. The results of these in vitro experiments suggest that the ester hydrolysis products of 2F-QMPSB and their glucuronides are suitable targets for toxicological screenings. In the case of SGT-233, the mono- and dihydroxy metabolites were identified as suitable screening targets. The involvement of various CYP isoforms in the metabolism of both substances reduces the likelihood of drug-drug interactions due to CYP inhibition.

A New Multi-Analyte LC-MS-MS Screening Method for the Detection of 120 NPSs and 49 Drugs in Hair

Liquid chromatography coupled with mass spectrometry (LC-MS) has been increasingly used for screening purposes in forensic toxicology. High versatility and low time/resource consumption are the main advantages of this technology. Numerous multi-analyte methods have been validated in order to face the analytical challenge of new psychoactive substances (NPSs). However, forensic toxicologists must focus the attention also on "classical" NPSs and medicines, such as benzodiazepines (BDZs) and prescription opioids. In this paper, a new method for the simultaneous detection of 169 substances (120 NPSs and 49 other drugs) in hair by LC-MS-MS is described. After the decontamination of hair samples with dichloromethane, a 20-mg aliquot of the sample was mixed with 1 mL of methanol (MeOH; 0.1% of formic acid) and then sonicated at room temperature for 2 h. The mixture was then dried under nitrogen stream and reconstituted with 100 µL of MeOH. LC separation was achieved with a 100-mm-long C18 column in 35 min, and mass acquisition was performed in dynamic multiple reaction monitoring mode and in positive ionization. The analysis results were very sensitive, with the limit of quantification ranging from 0.07 to 10.0 pg/mg. Accuracy and precision were always within the acceptable criteria. Matrix effect and recovery rate ranges were from -21.3 to + 21.9% and from 75.0 to 99.3%, respectively. The new method was successfully applied in a preliminary study on the prevalence of NPSs, BDZs and other substances in case of driving license issuance. In 14% of cases, BDZs/antidepressants (mainly trazodone, diazepam/nordiazepam and flunitrazepam) were found. Codeine, ketamine, methylone and mephedrone were also detected.

New Psychoactive Substances: Which Biological Matrix Is the Best for Clinical Toxicology Screening?

BACKGROUND

Every year, more new psychoactive substances (NPSs) emerge in the market of the drugs of abuse. NPSs belong to various chemical classes, such as synthetic cannabinoids, phenethylamines, opioids, and benzodiazepines. The detection of NPSs intake using different types of biological matrices is challenging for clinical toxicologists because of their structural diversity and the lack of information on their toxicokinetics, including their metabolic fate.

METHODS

PubMed-listed articles reporting mass spectrometry-based bioanalytical approaches for NPSs detection published during the past 5 years were identified and discussed. Furthermore, the pros and cons of using common biological matrices in clinical toxicology (CT) settings to screen for NPSs are highlighted in this review article.

RESULTS

Twenty-six articles presenting multianalyte screening methods for use in the field of CT were considered. The advantages and disadvantages of different biological matrices are discussed with a particular view of the different analytical tasks in CT, especially emergency toxicology. Finally, an outlook introduces the emerging trends in biosamples used in CT, such as the exhaled breath.

CONCLUSIONS

Blood and urine represent the most common biological matrices used in a CT setting; however, reports concerning NPSs detection in alternative matrices are also available. Noteworthy, the selection of the biological matrix must depend on the clinician's enquiry because the individual advantages and disadvantages must be considered.

Biochip Array Technology for new psychoactive substances detection in biological samples: evaluation of the specificity of the Randox Evidence Investigator®

Background The need to detect new psychoactive substances in biological samples is of crucial interest. In this paper, the specificity of a benchtop immunoanalyzer commercialized by Randox was evaluated on real patient samples. Method The Evidence Investigator was assessed to screen for NPS on 80 serum and urine samples coming from patient admitted to the emergency department. Targeted NPS were included in various categories such as synthetic cannabinoids, opioids and benzodiazepines. Results were compared with a chromatographic technique coupled with mass spectrometry. Results No NPS was detected by the reference technique. Concerning immunoanalysis, some piperazines were positive, caused by the presence of medicine containing this chemical structure. Clonazepam and fentanyl derivatives were confirmed in some cases, but sometimes the positivity was explained by other opiates or benzodiazepines, which also explained 2 samples falsely positive for etizolam. Conclusions The Randox Evidence Investigator was rapid and easy to use. It can be used as a first intention but always followed by a more specific technique in order to detect false positive result.

Deaths from novel psychoactive substances in England, Wales and Northern Ireland: Evaluating the impact of the UK psychoactive substances act 2016

BACKGROUND

'Legal highs' began appearing in the UK in the mid-2000s. Whilst many of these substances were controlled under the 1971 Misuse of Drugs Act, novel compounds and new variants of controlled compounds were continuously being introduced to the recreational drug market. The Psychoactive Substances Act (PSA) was therefore implemented in 2016 as a blanket ban on all novel psychoactive substances (NPS).

AIM

To evaluate the impact of the PSA on deaths following NPS use in England, Wales and Northern Ireland.

METHODS

Cases reported to the National Programme on Substance Abuse Deaths where death had occurred 3 years pre- or post-implementation of the PSA were extracted. Cases with NPS detected at post-mortem were analysed and compared against cases non-NPS cases.

RESULTS

293 deaths with NPS detected were identified; 91 occurring before the PSA and 202 afterwards, indicating an 222.0% post-PSA increase. Contrastingly, non-NPS drug-related death case reporting increased by only 8.0%. Synthetic cannabinoid, anxiolytic/sedative and stimulant NPS were detected in the largest proportions of deaths pre-PSA; post-PSA stimulant NPS detections reduced whilst synthetic cannabinoid and anxiolytic/sedative detections increased.Post-PSA, average decedent age increased significantly (mean age pre-PSA 34.4 ± 10.8 vs post-PSA 38.3 ± 9.4), and they were significantly more likely to have been living in deprived areas (pre-PSA 50.0% vs post-PSA 65.9%).

CONCLUSIONS

Reporting of deaths following NPS use has risen despite introduction of the PSA. Whilst deaths amongst younger individuals and those living in more affluent areas has reduced, additional approaches to prohibition are needed to curb their persistence in deprived demographics.

The Rise and Fall of Isotonitazene and Brorphine: Two Recent Stars in the Synthetic Opioid Firmament

Synthetic opioids constitute one of the fastest growing groups of new psychoactive substances (NPS) worldwide. With fentanyl analogues being increasingly controlled via class-wide scheduling, many non-fentanyl related opioids are now emerging on the recreational opioid market, rendering the landscape highly complex and dynamic. While new compounds are entering the supply in rapid and unpredictable manners, some recent patterns have become apparent. Many of these newly emerging opioids are being pirated from early patent literature and/or research papers, synthesized and sold online through various channels. Burdened by the identification of every newly emerging drug, many toxicology labs struggle to keep up. Moreover, by the time a "new" drug is controlled via legislative measures, illicit drug markets will have already adapted and diversified as manufacturers work to avoid the restricted product(s). Hence, the typical life-cycle of an NPS opioid is generally short (less than 6 months to one year), with only a few drugs escalating to significant numbers of detections. In this review, we summarize the key events in the emergence, rise, and subsequent decline of two non-fentanyl opioids - isotonitazene and brorphine. These two opioids sequentially dominated the NPS opioid market in 2019 and 2020. Both isotonitazene and brorphine remained in circulation for over a year, each contributing to hundreds of deaths and adverse events. By detailing the life-cycles of these opioids from their earliest synthesis as described in scientific literature to their subsequent rise and fall on recreational markets, this review illustrates the new characteristic life-cycle of synthetic opioids in the 'post-fentanyl-analogue' era.

Simultaneous LC-MS/MS screening for multiple phenethylamine-type conventional drugs and new psychoactive substances in urine

New psychoactive substances are being launched in the drug market at a rapidly growing pace. More than 950 new psychoactive substances have been reported to the United Nations Office on Drugs and Crime. The development of new psychoactive substance abuse has drawn risks on public health and safety. Phenethylamines, along with other stimulants, accounted for the majority of the new psychoactive substances being reported in the past decade. This study presents a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous screening of 74 conventional and artificial phenethylamines in urine samples. The chromatographic analysis was performed by a direct dilute-and-shoot procedure using a Phenomenex Kinetex® Phenyl-Hexyl column (10 cm × 2.1 mm i.d., 1.7 µm) and two mobile phases (A: 0.1% formic acid aqueous solution with 5 mM ammonium acetate, B: 0.1% formic acid methanolic solution). The mass fragments were collected under the multiple reaction monitoring mode. The linearity range located in 1.0-50.0 ng/mL for quantitative analysis. The limit of detection and lower limit of quantification for 74 phenethylamines were 0.5 ng/mL and 1.0 ng/mL, respectively. The method was validated and further applied to analyze authentic urine samples. Twenty samples were tested positive of seven phenethylamines from 67 samples, whereas the contents detected were 9.8 ng/mL to 147.1 μg/mL with dilution factors of 40 to 20,000 folds.

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

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.

Studies on the In Vitro and In Vivo Metabolic Fate of the New Psychoactive Substance N-Ethyl-N-Propyltryptamine for Analytical Purposes

Prerequisites for the reliable identification of substances in terms of forensic and clinical toxicology or doping control include knowledge about their metabolism and their excretion patterns in urine. N-Ethyl-N-propyltryptamine (N-ethyl-N-[2-(1H-indol-3-yl)ethyl]propan-1-amine, EPT) is an N,N-dialkylated tryptamine derivative, sold as new psychoactive substance, and supposed to act as a partial agonist at the 5-HT2A receptor. The aims of the presented study were to elucidate in vitro metabolites of EPT after incubations with pooled human liver S9 fraction (pS9) and in vivo metabolites excreted into rat urine. Finally, suitable analytical target compounds should be identified. Analysis of pS9 incubations using liquid chromatography-high-resolution tandem mass spectrometry revealed EPT metabolites formed after N-dealkylation as well as alkyl and aryl hydroxylation and formation of a hydroxy sulfate. Investigations using rat urine after oral dosing showed that the metabolic pathways of EPT shifted from in vitro hydroxylation of the alkyl amine group to an increased in vivo hydroxylation of the indole ring with several N-dealkyl metabolites. A glucuronic acid conjugate after hydroxylation of the indole ring was additionally found in vivo. The parent compound could not be detected in the rat urine samples. Therefore, analytical methods using mass spectrometry should include hydroxy-EPT and two hydroxy-EPT glucuronide isomers for reliable identification.

Current Status of Clinical Application of Point-of-Care Testing

CONTEXT.—

The clinical applications of point-of-care testing (POCT) are gradually increasing in many health care systems. Recently, POCT devices using molecular genetic method techniques have been developed. We need to examine clinical pathways to see where POCT can be applied to improve them.

OBJECTIVE.—

To introduce up-to-date POCT items and equipment and to provide the content that should be prepared for clinical application of POCT.

DATA SOURCES.—

Literature review based on PubMed searches containing the terms point-of-care testing, clinical chemistry, diagnostic hematology, and clinical microbiology.

CONCLUSIONS.—

If medical resources are limited, POCT can help clinicians make quick medical decisions. As POCT technology improves and menus expand, areas where POCT can be applied will also increase. We need to understand the limitations of POCT so that it can be optimally used to improve patient management.

Liquid Chromatography-High-Resolution Mass Spectrometry-Based In Vitro Toxicometabolomics of the Synthetic Cathinones 4-MPD and 4-MEAP in Pooled Human Liver Microsomes

Synthetic cathinones belong to the most often seized new psychoactive substances on an international level. This study investigated the toxicometabolomics, particularly the in vitro metabolism of 2-(methylamino)-1-(4-methylphenyl)-1-pentanone (4-MPD) and 2-(ethylamino)-1-(4-methylphenyl)-1-pentanone (4-MEAP) in pooled human liver microsomes (pHLM) using untargeted metabolomics techniques. Incubations were performed with the substrates in concentrations ranging from 0, 12.5, and 25 µM. Analysis was done by means of high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC-HRMS/MS) in full scan only and the obtained data was evaluated using XCMS Online and MetaboAnalyst. Significant features were putatively identified using a separate parallel reaction monitoring method. Statistical analysis was performed using Kruskal-Wallis test for prefiltering significant features and subsequent hierarchical clustering, as well as principal component analysis (PCA). Hierarchical clustering or PCA showed a distinct clustering of all concentrations with most of the features z-scores rising with the concentration of the investigated substances. Identification of significant features left many of them unidentified but revealed metabolites of both 4-MPD and 4-MEAP. Both substances formed carboxylic acids, were hydroxylated at the alkyl chain, and formed metabolites after combined hydroxylation and reduction of the cathinone oxo group. 4-MPD additionally formed a dihydroxy metabolite and a hydroxylamine. 4-MEAP was additionally found reduced at the cathinone oxo group, N-dealkylated, and formed an oxo metabolite. These findings are the first to describe the metabolic pathways of 4-MPD and to extend our knowledge about the metabolism of 4-MEAP. Findings, particularly the MS data of the metabolites, are essential for setting up metabolite-based toxicological (urine) screening procedures.

A Comprehensive HPLC-MS-MS Screening Method for 77 New Psychoactive Substances, 24 Classic Drugs and 18 Related Metabolites in Blood, Urine and Oral Fluid

To date, more than 800 molecules are classified as New Psychoactive Substances (NPS), and it is reported that this number increases every year. Whereas several cases of polydrug consumption that led to acute intoxication and death are reported, a lack of effective analytical screening method to detect NPS and classical drug of abuse in human matrices affects the prompt identification of the probable cause of intoxication in emergency department of hospitals. In this concern, a fast, simple and comprehensive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) screening method to detect and quantify 77 NPS, 24 classic drugs and 18 related metabolites has been successfully developed and validated in blood, urine and oral fluid. A small volume (100 µL) of whole blood samples spiked with internal standard deuterated mixture was added to 70 µL of M3® buffer, and after precipitation of blood proteins, the supernatant was evaporated to dryness and reconstituted in 1 mL of mobile phase. Same volume (100 µL) of urine and oral fluid samples spiked with internal standard deuterated mix were only diluted with 500 µL of M3® reagent. One microliter of samples of each matrix was injected into HPLC-MS-MS equipment. The run time lasted 10 min with a gradient mobile phase. Mass spectrometric analysis was performed in positive ion multiple reaction monitoring mode. The method was linear for all analytes under investigation with a determination coefficient always better than 0.99. The calibration range for blood and oral fluid was from limits of quantification (LOQs) to 200 ng/mL, whereas that for urine was LOQs to 1000 ng/mL. Recovery and matrix effect were always higher than 80%, whereas intra-assay and inter-assay precision were always better than 19% and accuracy was always within 19% of target in every matrix. Applicability of the method was verified by analysis of samples from real cases.

Optimization and validation of a new approach based on CE-HRMS for the screening analysis of novel psychoactive substances (cathinones, phenethylamines, and tryptamines) in urine

The continuous introduction in the market of new psychoactive drugs (NPS) represents a well-known international emergency. Indeed, the European Monitoring Centre for Drugs and Drug Addiction and the United Nations Office on Drugs and Crime are paying great attention to the spread of NPS. In addition to the traditional analytical approaches based on GC-MS and HPLC-MS, also CE coupled with MS has proved to be a precious tool for the toxicological screening of biosamples. On these grounds, the aim of the present work was to test the application of CE-HRMS as a new screening tool for the rapid detection of these novel drugs in urine. Separations were performed in an uncoated fused-silica capillary with id of 75 μm with a total length of 100 cm, by applying a constant voltage of 15 kV. The QTOF-MS was implemented with an electrospray ion source operating in positive ionization full scan mode in the range of 100-1000 m/z. Under these conditions, different NPS has been tested, including eight cathinones, five phenethylamine, and seven tryptamines. The method was validated after optimization of the following analytical parameters: BGE composition and pH, separation voltage, sheath liquid composition, and flow rate and ESI source settings. The applicability of the method was successfully tested by analyzing a series of real urine samples obtained from drug users.

Hyphenated high-resolution mass spectrometry-the "all-in-one" device in analytical toxicology?

This trend article reviews papers with hyphenated high-resolution mass spectrometry (HRMS) approaches applied in analytical toxicology, particularly in clinical and forensic toxicology published since 2016 and referenced in PubMed. The article focuses on the question of whether HRMS has or will become the all-in-one device in these fields as supposed by the increasing number of HRMS presentations at scientific meetings, corresponding original papers, and review articles. Typical examples for the different application fields are discussed such as targeted or untargeted drug screening, quantification, drug metabolism studies, and metabolomics approaches. Considering the reviewed papers, HRMS is currently the only technique that fulfills the criteria of an all-in-one device for the various applications needed in analytical toxicology.

Graphical abstract

Recent bionalytical methods for the determination of new psychoactive substances in biological specimens

One of the problems associated with the consumption of new psychoactive substances is that in most scenarios of acute toxicity the possibility of quick clinical action may be impaired because many screening methods are not responsive to them, and laboratories are not able to keep pace with the appearance of new substances. For these reasons, developing and validating new analytical methods is mandatory in order to efficiently face those problems, allowing laboratories to be one step ahead. The goal of this work is to perform a critical review regarding bionalytical methods that can be used for the determination of new psychoactive substances (phenylethylamines, cathinones, synthetic cannabinoids, opioids, benzodiazepines, etc), particularly concerning sample preparation techniques and associated analytical methods.

How to Study the Metabolism of New Psychoactive Substances for the Purpose of Toxicological Screenings-A Follow-Up Study Comparing Pooled Human Liver S9, HepaRG Cells, and Zebrafish Larvae

The new psychoactive substances (NPS) market continues to be very dynamic. A large number of compounds belonging to diverse chemical groups continue to emerge. This makes their detection in biological samples challenging for clinical and forensic toxicologists. Knowledge of the metabolic fate of NPS is crucial for developing comprehensive screening procedures. As human studies are not feasible due to ethical concerns, the current study aimed to compare the NPS' metabolic pattern in incubations with pooled human liver S9 fraction (pHLS9), human liver HepaRG cells, and zebrafish larvae. The latter model was recently shown to be a promising preclinical surrogate for human hepatic metabolism of a synthetic cannabinoid. However, studies concerning other NPS classes are still missing and therefore an amphetamine-based N-methoxybenzyl (NBOMe) compound, a synthetic cathinone, a pyrrolidinophenone analog, a lysergamide, as well as another synthetic cannabinoid were included in the current study. Liquid chromatography coupled to Orbitrap-based high-resolution tandem mass spectrometry was used to analyze metabolic data. Zebrafish larvae were found to produce the highest number of phase I but also phase II metabolites (79 metabolites in total), followed by HepaRG cells (66 metabolites). Incubations with pHLS9 produced the least metabolites (57 metabolites). Furthermore, the involvement of monooxygenases and esterases in the metabolic phase I transformations of 4F-MDMB-BINACA was elucidated using single-enzyme incubations. Several cytochrome P450 (CYP) isozymes were shown to contribute, and CYP3A5 was involved in all CYP-catalyzed reactions, while amide and ester hydrolysis were catalyzed by the human carboxylesterase (hCES) isoforms hCES1b and/or hCES1c. Finally, metabolites were compared to those present in human biosamples if data were available. Overall, the metabolic patterns in HepaRG cells provided the worst overlap with that in human biosamples. Zebrafish larvae experiments agreed best with data found in human plasma and urine analysis. The current study underlines the potential of zebrafish larvae as a tool for elucidating the toxicokinetics of NPS in the future.

Toxicokinetics and toxicodynamics of the fentanyl homologs cyclopropanoyl-1-benzyl-4´-fluoro-4-anilinopiperidine and furanoyl-1-benzyl-4-anilinopiperidine

The two fentanyl homologs cyclopropanoyl-1-benzyl-4´-fluoro-4-anilinopiperidine (4F-Cy-BAP) and furanoyl-1-benzyl-4-anilinopiperidine (Fu-BAP) have recently been seized as new psychoactive substances (NPS) on the drugs of abuse market. As their toxicokinetic and toxicodynamic characteristics are completely unknown, this study focused on elucidating their in vitro metabolic stability in pooled human liver S9 fraction (pHLS9), their qualitative in vitro (pHLS9), and in vivo (zebrafish larvae) metabolism, and their in vitro isozyme mapping using recombinant expressed isoenzymes. Their maximum-tolerated concentration (MTC) in zebrafish larvae was studied from 0.01 to 100 µM. Their µ-opioid receptor (MOR) activity was analyzed in engineered human embryonic kidney (HEK) 293 T cells. In total, seven phase I and one phase II metabolites of 4F-Cy-BAP and 15 phase I and four phase II metabolites of Fu-BAP were tentatively identified by means of liquid chromatography high-resolution tandem mass spectrometry, with the majority detected in zebrafish larvae. N-Dealkylation, N-deacylation, hydroxylation, and N-oxidation were the most abundant metabolic reactions and the corresponding metabolites are expected to be promising analytical targets for toxicological analysis. Isozyme mapping revealed the main involvement of CYP3A4 in the phase I metabolism of 4F-Cy-BAP and in terms of Fu-BAP additionally CYP2D6. Therefore, drug-drug interactions by CYP3A4 inhibition may cause elevated drug levels and unwanted adverse effects. MTC experiments revealed malformations and changes in the behavior of larvae after exposure to 100 µM Fu-BAP. Both substances were only able to produce a weak activation of MOR and although toxic effects based on MOR activation seem unlikely, activity at other receptors cannot be excluded.

Use of UPLC-HRMS/MS for In Vitro and In Vivo Metabolite Identification of Three Methylphenidate-derived New Psychoactive Substances

The distribution of so-called new psychoactive substances (NPS) as substitute for common drug of abuse was steadily increasing in the last years, but knowledge about their toxicodynamic and toxicokinetic properties is lacking. However, a comprehensive knowledge of their toxicokinetics, particularly their metabolism, is crucial for developing reliable screening procedures and to verify their intake, e.g., in case of intoxications. The aim of this study was therefore to tentatively identify the metabolites of the methylphenidate-derived NPS isopropylphenidate (isopropyl 2-phenyl-2-(2-piperidyl) acetate, IPH), 4-fluoromethylphenidate (methyl 2-(4-fluorophenyl)-2-(piperidin-2-yl) acetate, 4-FMPH) and 3,4-dichloromethylphenidate (methyl 2-(3,4-dichlorophenyl)-2-(piperidin-2-yl) acetate, 3,4-CTMP) using different in vivo and in vitro techniques and ultra-high performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS/MS). Urine samples of male rats were analyzed, and the transfer to human metabolism was done by using pooled human S9 fraction (pS9), which contains the microsomal fraction of liver homogenisate as well as its cytosol. UHPLC-HRMS/MS analysis of rat urine revealed 17 metabolites for IPH (14 phase I and 3 phase II metabolites), 13 metabolites were found for 4-FMPH (12 phase I metabolites and 1 phase II metabolite) and 7 phase I metabolites and no phase II metabolites were found for 3,4-CTMP. pS9 incubations additionally indicated that all investigated substances were primarily hydrolyzed, resulting in the corresponding carboxy metabolites. Finally, these carboxy metabolites should be used as additional analytical targets besides the parent compounds for comprehensive mass spectrometry-based screening procedures.

Toxicokinetics and Analytical Toxicology of Flualprazolam: Metabolic Fate, Isozyme Mapping, Human Plasma Concentration and Main Urinary Excretion Products

An increasing number of benzodiazepine-type compounds are appearing on the new psychoactive substances market. 8-Chloro-6-(2-fluorophenyl)-1-methyl-4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepine (well known as flualprazolam) represents a potent ‘designer benzodiazepine’ that has been associated with sedation, loss of consciousness, memory loss and disinhibition. The aims of the present study were to tentatively identify flualprazolam metabolites using in vitro incubations with pooled human liver S9 fraction or HepaRG cells by means of liquid-chromatography-high resolution tandem mass spectrometry. Isozymes involved in phase I and II biotransformation were identified in vitro. Results were then confirmed using human biosamples of an 18-year old male who was admitted to the emergency department after suspected flualprazolam ingestion. Furthermore, the plasma concentration was determined using the standard addition method. Seven flualprazolam metabolites were tentatively identified. Several cytochrome P450 and UDP-glucuronosyltransferase isozymes, amongst them CYP3A4 and UGT1A4, were shown to be involved in flualprazolam biotransformation reactions, and an influence of polymorphisms as well as drug–drug or drug–food interactions cannot be excluded. Alpha-hydroxy flualprazolam glucuronide, 4-hydroxy flualprazolam glucuronide and the parent glucuronide were identified as most abundant signals in urine, far more abundant than the parent compound flualprazolam. These metabolites are thus recommended as urine-screening targets. If conjugate cleavage was performed during sample preparation, the corresponding phase I metabolites should be added as targets. Both hydroxy metabolites can also be recommended for blood screening. The flualprazolam plasma concentration determined in the intoxication case was as low as 8 μg/L underlining the need of analytical methods with sufficient sensitivity for blood-screening purposes.

Toxicokinetic Studies and Analytical Toxicology of the New Synthetic Opioids Cyclopentanoyl-Fentanyl and Tetrahydrofuranoyl-Fentanyl

The growing number of new synthetic opioids (NSO) on the new psychoactive substances (NPS) market bears new challenges in toxicology. As their toxicodynamics and particularly their toxicokinetics are usually unknown, impact on human health is not yet fully understood. Detection of the 2 NSO cyclopentanoyl-fentanyl (CP-F) and tetrahydrofuranoyl-fentanyl (THF-F) was first reported in 2016. Both were involved in several fatal intoxication cases, but no detailed information about their toxicological characteristics is available so far. The main purpose of this study was therefore to investigate the in vitro toxicokinetics and in vivo analytical toxicology of CP-F and THF-F by means of liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). These studies included metabolic stability, phase I and II metabolism, isozyme mapping, plasma protein binding and detectability in LC-HRMS/MS standard urine screening approaches (SUSA) using rat urine samples. In total, 12 phase I metabolites of CP-F and 13 of THF-F were identified, among them 9 metabolites described for the first time. Overall, N-dealkylations, hydroxylations and dihydroxylations were the main metabolic reactions. The cytochrome P450 (CYP) isozymes mainly involved were CYP2D6 and CYP3A4, leading to elevated drug levels and intoxications in CYP2D6 poor metabolizers. CP-F showed a high plasma protein binding of 99%, which may increase the risk of toxicity by simultaneous intake of other highly bound drugs. Detectability studies showed that neither the parent compounds nor their metabolites were detectable in rat urine using LC-HRMS/MS SUSA. However, a more sophisticated analytical strategy was successfully applied and should be used for analytical confirmation of an intake of CP-F and/or THF-F.

Pitfalls in drug testing by hyphenated low- and high-resolution mass spectrometry

This paper reviews various pitfalls observed during developing, validation, application, and interpretation of drug testing approaches using GC-MS and low- and high-resolution LC-MS. They include sampling and storage of body samples, sample adulteration and contamination, analyte stability, sample preparation without or with cleavage of conjugates, extraction, derivatization, internal standardization, false negative and positive results by GC-MS or LC-MS screening and/or confirmation procedures including artifact formation, ion suppression or enhancement by electrospray ionization, and finally pitfalls in data interpretation. Conclusions and prospects close the Tutorial.

Clinical value of analytical testing in patients presenting with new psychoactive substances intoxication

New psychoactive substances (NPS) have emerged worldwide in recent years, posing a threat to public health and a challenge to drug policy. NPS are usually derivatives or analogues of classical recreational drugs designed to imitate their effects while circumventing regulations. This article provides an overview of benefits and limitations of analytical screening in managing patients presenting with acute NPS toxicity. NPS typically cannot be analytically identified with the usual immunoassay tests. To detect NPS using an immunoassay, antibodies specifically binding to the new structures would have to be developed, which is complicated by the rapid change of the NPS market. Activity-based assays could circumvent this problem since no prior knowledge on the substance structure is necessary. However, classical recreational drugs activating the same receptors could lead to false positive results. Liquid or gas chromatography coupled with mass spectrometry is a valuable NPS analysis tool, but its costs (e.g. equipment), run time (results usually within hours vs minutes in case of immunoasssays) and the need for specialized personnel hinder its use in clinical setting, while factors such as lack of reference standards can pose further limitations. Although supportive measures are sufficient in most cases for adequate patient management, the detection and identification of NPS can contribute significantly to public health and safety in cases of e.g. cluster intoxications and outbreaks, and to the investigation of these novel compounds' properties. However, this requires not only availability of the necessary equipment and personnel, but also collaboration between clinicians, authorities and laboratories.

Mass Spectrometry for Research and Application in Therapeutic Drug Monitoring or Clinical and Forensic Toxicology

This article reviews current applications of various hyphenated low- and high-resolution mass spectrometry techniques in the field of therapeutic drug monitoring and clinical/forensic toxicology in both research and practice. They cover gas chromatography, liquid chromatography, matrix-assisted laser desorption ionization, or paper spray ionization coupled to quadrupole, ion trap, time-of-flight, or Orbitrap mass analyzers.

Screening methods for rapid determination of new psychoactive substances (NPS) in conventional and non-conventional biological matrices

In the last years, a global awareness has arisen from the reported harmful effects and public health risks associated with the consumption of new psychoactive substances (NPSs). Improving efforts in the detection and identification of these substances have emerged as a global analytical challenge involving the large range of NPSs' chemical structures and the variety of conventional and non-conventional biological matrices. Indeed, detection capabilities and screening tools impact many fields and settings, including seized products analysis, workplace and roadside drug controls, emergency rooms, drug addiction treatment clinics, post-mortem and criminal caseworks, law enforcement and health interventions. Colorimetric, immunochemical and chromatographic-mass spectrometry techniques have been investigated and developed for the rapid identification of NPSs. Considering the continuous emergence of new substances, this review offers a panoramic view on the current status of analytical approaches for the rapid screening of NPSs, including, when available, data on conventional and non-conventional biological matrices. Although some of the presented methods are sound and promising, their applications are still limited, thus proving the importance of further investigations. New screening and sensitive targeted methods for NPS and their metabolites should be developed in different types of biological matrices, where concentration of substances and matrix effects can be significantly different.

Interactions of phenethylamine-derived psychoactive substances of the 2C-series with human monoamine oxidases

Psychoactive substances of the 2C-series (2Cs) are phenethylamine-derived designer drugs that can induce psychostimulant and hallucinogenic effects. Chemically, the classic 2Cs contain two methoxy groups in positions 2 and 5 of the phenyl ring, whereas substances of the so-called FLY series contain rigidified methoxy groups integrated in a 2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran core. One of the pharmacological features that has not been investigated in detail is the inhibition of monoamine oxidase (MAO). Inhibition of this enzyme can cause elevated monoamine levels that have been associated with adverse events such as agitation, nausea, vomiting, tachycardia, hypertension, or seizures. The aim of this study was to extend the knowledge surrounding the potential of MAO inhibition for 17 test drugs, which consisted of 12 2Cs (2C-B, 2C-D, 2C-E, 2C-H, 2C-I, 2C-N, 2C-P, 2C-T-2, 2C-T-7, 2C-T-21, bk-2C-B, and bk-2C-I) and five FLY analogs (2C-B-FLY, 2C-E-FLY, 2C-EF-FLY, 2C-I-FLY, and 2C-T-7-FLY). The extent of MAO inhibition was assessed using an established in vitro procedure based on heterologously expressed enzymes and analysis by hydrophilic interaction liquid chromatography-high resolution tandem mass spectrometry. Thirteen test drugs showed inhibition potential for MAO-A and 11 showed inhibition of MAO-B. In cases where MAO-A IC₅₀ values were determined, values ranged from 10 to 125 μM (7 drugs) and from 1.7 to 180 μM for MAO-B (9 drugs). In the absence of detailed clinical information on most test drugs, it is concluded that a pharmacological contribution of MAO inhibition cannot be excluded and that further studies are warranted.

Patterns of Acute Toxicity Associated with New Psychoactive Substances

This chapter begins by considering why it is important to understand the clinical patterns of acute toxicity associated with new psychoactive substances (NPS), the challenges associated with gathering these data, the sources of information available and the limitations of each. It describes the data triangulation approach that can be used to combine individual, each inherently limited, data sources to help build the picture of the pattern of acute non-fatal toxicity associated with NPS. The chapter illustrates the data triangulation approach by the use of clinical examples and aims to consider mechanism of action data in conjunction with clinical features to provide an overarching understanding of the clinical presentation. Examples of the most important individual and groups of NPS were identified using multimodal literature searching based on the most relevant terms. The chapter provides descriptive accounts that are a complete reference source on the patterns of acute toxicity.