Stability of synthetic cathinones in clinical and forensic toxicological analysis-Where are we now?

Challenges encountered in the enantioselective analysis of new psychoactive substances exemplified by clephedrone (4-CMC)

In this study we report on efforts to develop an enantioselective method for the detection of the drug of abuse clephedrone (1-(4-chlorophenyl)-2-(methylamino)-1-propanone (4-chloromethcathinone, also known as 4-CMC or para-chloro-methcathinone)) and its phase-1 metabolites in human biological fluids. The major goal is not to only report results, but primarily to emphasize the various challenges encountered when developing a reliable analytical method for the detection and quantification of novel psychoactive substances (NPS) and their metabolites in the matrix of interest. Such challenges start with the lack of chemical stability of some NPS in biological matrices. Additionally, most often metabolites are unavailable in pure form to serve as analytical standards, just as deuterated standards for native drugs and metabolites are frequently not commercially available. Furthermore, if the NPS is chiral, enantiomerically pure standards with known absolute stereochemistry are required, as well as a stereochemical stability of a drug and its metabolites becomes an issue. In addition, the chirality of a NPS significantly increases the number of species to be detected in the sample and thus challenges the development of an adequate separation method. These issues are shortly addressed, and some solutions offered in this manuscript.

Structure-Activity Relationship of Synthetic Cathinones: An Updated Review

The escalating prevalence of new psychoactive substances (NPSs) poses a significant public health challenge, evidenced by the vast chemical diversity, with over 500 substances reported annually to the United Nations Office on Drugs and Crime-Early Warning Advisory (UNODC-EWA) in the past five years. Among NPSs, synthetic cathinones are gaining a lot of popularity among users. Notably, synthetic cathinones accounted for approximately 50% of the total quantity of NPSs reported as seized by EU Member States in 2021. Preliminary data from UNODC indicates that a total of 209 synthetic cathinones have been reported to date. As their popularity grows, studying the structure-activity relationship (SAR) of synthetic cathinones is essential. SAR studies elucidate how structural features impact biological effects, aiding in toxicity prediction, regulatory compliance, and forensic identification. Additionally, SAR studies play a pivotal role in guiding drug policies, aiding authorities in categorizing and regulating newly emerging synthetic cathinones, mitigate public health risks and offer valuable insights into potential therapeutic applications. Thus, our Review consolidates recent findings on the effects of different substitutions in the chemical scaffold of synthetic cathinones on their mechanism of action as well as pharmacological and toxicological effects of synthetic cathinones, thus enhancing understanding of the SAR of synthetic cathinones' pharmacology and potential implications.

Short- and long-term stability of synthetic cathinones and dihydro-metabolites in human urine samples

PURPOSE

Synthetic cathinones constitute the second largest group of new psychoactive substances, which are often used for recreational purposes and reported in toxicological analysis. Various factors may influence the stability of synthetic cathinones between sampling and analysis, and therefore, stability studies are required to determine the best storage conditions as well as extend the period of detection.

METHODS

This study involved sixteen synthetic cathinones and ten dihydro-metabolites spiked in human urine to evaluate the stability under common storage conditions to imitate real forensic toxicology samples. The samples were stored at either room temperature (22-23 °C) for up to 3 days, refrigerated (4 °C) for up to 14 days or frozen (-40 °C) for up to 12 months, and analyzed in triplicate using a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Analytes' concentrations decreased over time, although slower when stored frozen. All analytes remained stable (> 80%) for 1 month when stored frozen before losses in content were more apparent for some compounds, depending on their chemical structure. Under all storage conditions, the highest instability was observed for analytes containing halogens (i.e., chlorine or fluorine). Thus, halogenated analytes were further investigated by using liquid chromatography coupled to quadruple time-of-flight mass spectrometry to attempt identifying degradation products.

CONCLUSIONS

Irrespective of parent analytes, dihydro-metabolites had improved stability at each tested temperature, which highlights their importance as appropriate urine biomarkers when retesting is required after a long period of storage.

Drug-Modified Contact Lenses-Properties, Release Kinetics, and Stability of Active Substances with Particular Emphasis on Cyclosporine A: A Review

The following review focuses on the manufacturing and parameterizing of ocular drug delivery systems (DDS) using polymeric materials to create soft contact lenses. It discusses the types of drugs embedded into contact lenses, the various polymeric materials used in their production, methods for assessing the mechanical properties of polymers, and techniques for studying drug release kinetics. The article also explores strategies for investigating the stability of active substances released from contact lenses. It specifically emphasizes the production of soft contact lenses modified with Cyclosporine A (CyA) for the topical treatment of specific ocular conditions. The review pays attention to methods for monitoring the stability of Cyclosporine A within the discussed DDS, as well as investigating the influence of polymer matrix type on the stability and release of CyA.

Clinical manifestations and analytical reports for MDPHP acute intoxication cases

MDPHP is a synthetic cathinone (SC) belonging to α-pyrrolidinophenone derivatives. It is a central nervous system stimulant and may induce hallucinations, paranoia, tachycardia, hypertension, chest pain, and rhabdomyolysis. In literature, a few cases of intoxication have been reported. In the present study, 17 cases of MDPHP intake were described including the analytical findings and clinical manifestations. MDPHP was quantified by liquid chromatography-tandem mass spectrometry in blood (range 1.26-73.30 ng/mL) and urine (range 19.31-8769.64 ng/mL) samples. In three cases the presence of α-PHP was observed. In one case, MDPHP was the only detected substance. Concomitant use of MDPHP with other substances, particularly psychostimulants, was common and it was difficult to describe the peculiar clinical characteristics of this SC. Most of the symptoms overlapped those expected, some of them were unusual and all of them particularly severe thus inducing the research of NPS in laboratory tests. We demonstrated the presence of psychiatric, neurological, and respiratory symptoms, as well as the possible presence of rhabdomyolysis and cardiotoxicity associated with the use of MDPHP. ED admissions were also more frequent in patients with addiction problems. In some cases, MDPHP intake required intensive supportive care. A multidisciplinary approach, including specialist consultation, is recommended for patients showing challenging features. Moreover, we demonstrated that the adoption of advanced analytical techniques, i.e., liquid chromatography-tandem mass spectrometry, is necessary to detect these molecules. Further studies are needed to understand MDPHP intake patterns and associated symptoms. It is essential to raise awareness in addiction treatment centers and among potential users, especially young people, and chemsex addicted.

3-Methylmethcathinone Intoxication: Discrepancies Between Blood Concentrations and Clinical Outcomes-A Short Communication

BACKGROUND

The absence of a correlation between the blood concentration of 3-methylmethcathinone (3-MMC) and clinical outcomes in intoxication cases has been attributed to stability issues. Indeed, a loss of more than 50%, 70%, and even 95% of 3-MMC in whole blood after 2 weeks of storage at 20°C, 4°C, and room temperature, respectively, has been reported in the past. Here, the authors report the case of a 43-year-old man who was hospitalized with generalized convulsive status epilepticus related to 3-MMC use with a plasma concentration of 9600 ng/mL (delay between sampling and analysis <72 hours). The stability of 3-MMC was evaluated in several biological specimens.

METHODS

Three quality control samples (human plasma, whole blood, and postmortem blood) spiked with 3-MMC were stored at -20°C and 4°C for 14 days. The initial analysis was performed on day 1 to establish the initial concentration of 3-MMC in each specimen type, and the samples were divided into 2 aliquots for storage under both conditions. Further analyses were performed on days 7 and 14 for each specimen, and the results were compared with those obtained on day 1.

RESULTS

3-MMC appeared relatively stable in whole and postmortem blood when stored at -20°C for 1 week, with losses of <3% in both matrices (0% and 2.5%, respectively). At +4°C, 3-MMC losses ranged from 25% to 53%.

CONCLUSIONS

These results differ from others reported in the literature. Hence, it may be hypothesized that other elements should be considered to explain the discrepancy between the concentration and toxicity pointed out by the Toxicology community, especially the development of tolerance.

Study on the degradation and pyrolysis of 2-fluoromethcathinone

Gas chromatography-mass spectrometry (GC-MS) is the first choice for law enforcement agencies in various countries to analyze new psychoactive substances (NPS) because of its advantages and complete databases. For synthetic cathinone-type NPS (SCat), alkalization and extraction processes before GC-MS analysis are essential. However, the base form of SCat is unstable, causing it to quickly degrade in solution and cause pyrolysis at the GC-MS injection inlet. In this study, we investigated the degradation of ethyl acetate and pyrolysis at the GC-MS injection inlet of 2-fluoromethcathinone (2-FMC), the most unstable SCat. Using gas chromatography-quadruple/time-of-flight mass spectrometry (GC-Q/TOF-MS) combined with the predicted data from theoretical calculations and the analysis of mass spectrometry (MS) fragmentation, the structures of 15 2-FMC degradation and pyrolysis products were identified. Among them, 11 products were produced during degradation, and six products were obtained from pyrolysis (two of which were the same as the degradation products). At the same time, the degradation and pyrolysis pathways of 2-FMC were provided. The balance between keto-enol and enamine-imine tautomerism triggered the primary degradation pathway of 2-FMC. The subsequent degradation started from the tautomer with a hydroxyimine structure, including imine hydrolysis, oxidation, imine-enamine tautomerism, intramolecular ammonolysis of halobenzene, and hydration to generate a series of degradation products. The secondary degradation reaction was the ammonolysis of ethyl acetate to yield N-[1-(2'-fluorophenyl)-1-oxopropan-2-yl]-N-methylacetamide and the byproduct, N-[1-(2'-fluorophenyl)-1-oxopropan-2-yl]-N-methylformamide. In the pyrolysis of 2-FMC, the major reactions were dehydrogenation, intramolecular ammonolysis of halobenzene, and defluoromethane. The achievements of this manuscript not only study 2-FMC degradation and pyrolysis but also lay the foundation for the study of SCat stability and their accurate analysis by GC-MS.

Simultaneous Determination and Stability Analysis of Ten New Psychoactive Substances including Synthetic Cathinones, Phenethylamines, and Ketamine Substitutes in Urine Using Liquid Chromatography-Tandem Mass Spectrometry

Knowing the stability of drugs is important to ensure accurate and reliable results of drug concentrations. This study evaluated the stability of ten new psychoactive substances (NPSs) in urine and methanol/water at different storage temperatures. Quantitative analyses were performed using liquid chromatography-tandem mass spectrometry. Three replicates of each storage condition were analyzed at day 0 and after 7, 14-, 30-, 60-, and 90 days with storage at +25°C, +4°C, and -20°C. For each analyte, the percent difference at each time interval from day 0 was calculated for each storage condition. Para-methoxyamphetamine (PMA), para-methoxymethamphetamine (PMMA), deschloroketamine (DCK), and 2-fluorodeschloroketamine (2-FDCK) were stable in urine, even when stored for 90-day periods at various temperatures. For synthetic cathinones, the concentrations declined over time at room temperature (+25°C) in urine but were relatively stable in methanol solvent with 0.1% formic acid. The significant degradation was found at +25°C, and the most excellent stability was shown by samples stored at -20°C. Phenethylamines (PMA and PMMA) and ketamine substitutes (DCK and 2-FDCK) were relatively more stable than synthetic cathinones (mephedrone, butylone, pentylone, ephylone, 4-MEAPP, and eutylone).

Acute, chronic, and post-mortem toxicity: a review focused on three different classes of new psychoactive substances

PURPOSE

New psychoactive substances (NPS) are not controlled under the Single Convention on Narcotic Drugs of 1961 or the 1971 Convention, but they may pose a public health threat. Knowledge of the main properties and toxicological effects of these substances is lacking. According to the current Drugs Law (Law n. 11.343/2006), the Brazilian Surveillance Agency issues directives for forbidden substances in Brazil, and structural classes of synthetic cannabinoids, cathinones, and phenylethylamines are considered illicit drugs. Considering that data on these controlled substances are scattered, the main objective of this work was to collect and organize data to generate relevant information on the toxicological properties of NPS.

METHODS

We carried out a literature review collecting information on the acute, chronic, and post-mortem toxicity of these classes of NSP. We searched info in five scientific databases considering works from 2017 to 2021 and performed a statistical evaluation of the data.

RESULTS

Results have shown a general lack of studies in this field given that many NPS have not had their toxicity evaluated. We observed a significant difference in the volume of data concerning acute and chronic/post-mortem toxicity. Moreover, studies on the adverse effects of polydrug use are scarce.

CONCLUSIONS

More in-depth information about the main threats involving NPS use are needed.

Frequency of new psychoactive substances in hair and urine samples of individuals subject to drug testing in driving license regranting-A toxicological perspective

In recent years, numerous new psychoactive substances (NPS) have emerged on the illicit drug market. The assumed non-detectability of these drugs is often a key motivation for individuals subject to drug testing, such as those in driving license regranting programs. In these programs, NPS are not routinely tested for, and thus, subjects who have to prove abstinence from common drugs of abuse might switch to NPS to avoid positive drug tests. The aim of the study was to determine the frequency of these substances in the hair and urine samples of individuals undergoing drug testing in driving license regranting. A total of 1037 samples (577 hair and 460 urine samples) collected from 949 subjects between February 2017 and December 2018 were retrospectively analyzed for designer drugs and synthetic cannabinoids by liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-QTOF-MS). For a more sensitive analysis of synthetic cannabinoids and their metabolites, additional testing was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Overall, 42 hair and two urine samples, which were obtained from 40 subjects, tested positive for NPS resulting in a frequency of 4.2%. While synthetic cannabinoids were detected in all cases, designer drugs were only found in three of these cases. With regard to the 577 hair samples analyzed, 7.3% screened positive, whereas only 0.4% of the 460 tested urine samples contained NPS. The results of this study indicate that synthetic cannabinoid use seems to be popular among this population, and therefore, testing for synthetic cannabinoids should be requested more often preferably using hair analysis.

Development and validation of a chiral LC-MS/MS method for the separation and quantification of four synthetic cathinones in human whole blood and its application in stability analysis

Synthetic cathinones, a subclass of new psychoactive substances, have gained high popularity on the recreational drugs market over the past years. These drugs typically have a chiral center, so they may exist as two stereoisomers. Therefore the pharmacological, pharmacokinetic or metabolic properties of their enantiomers are expected to differ. However, these drugs are often synthesized and sold as a racemic mixture, and as a consequence, differentiation of their (R)- and (S)- enantiomers is relevant in clinical and forensic toxicology. Information about single enantiomers of synthetic cathinones is relatively scarce due to challenges of their chiral analysis. Hence, a sensitive and reliable liquid chromatography-tandem mass spectrometry method was developed and validated for the chiral separation and quantification of four synthetic cathinones in human whole blood samples. The method was fully validated in terms of linearity, limit of detection, limit of quantification, bias, precision, carryover, interferences, matrix effects, recovery and processed sample stability and successfully applied to evaluate the stability as well as enantioselective degradation of synthetic cathinones enantiomers under various storage conditions. For most of the analytes, significant enantioselective degradation was observed when stored at room temperature or refrigerated, with the E2-enantiomers observed to more rapidly degrade under both conditions. This is the first report concerning the stability and enantioselective degradation of synthetic cathinone enantiomers in whole blood. Moreover, the inversion study demonstrated enantiomeric inversion of R-(-)- and S-(+)-methylenedioxypyrovalerone (MDPV) in human whole blood and methanolic solution.

Defective determination of synthetic cathinones in blood for forensic investigation

Antemortem specimens are sometimes the sole sources available for forensic investigation, and samples collected in nonideal ways are inevitably employed to achieve toxicological analysis. It is essential to assess the effects of blood collection tubes on the recoveries of emerging synthetic cathinones (SC) to estimate actual drug concentrations, and no such systematic investigations have been previously carried out. Seventy-one SC with various LogP values were employed to examine commonly used blood collection tubes, including plasma tubes, serum tubes and gel-containing tubes in recoveries which determined by a reliable LC-MS/MS method. Significantly poor recoveries for hydrophobic SC were obtained using serum separating tubes (SST). Notably, the suppressed recoveries in SST can be reversed by adding anticoagulants. Adding a procoagulant to a plasma separating tube (PST) considerably reduced recoveries, which indicated that clotting processes in the presence of polymeric gels contributed to poor recoveries of these hydrophobic drugs. In this study, we find that clotting formation in the presence of polymeric gels could significantly affect the determination of hydrophobic drugs. However, in real-world scenarios, nonideal collection methods are inevitably employed for antemortem specimens. Thus, it is important to rigorously interpret forensic toxicological results, especially for susceptible species.

Influence of long-term storage temperatures and sodium fluoride preservation on the stability of synthetic cathinones and dihydro-metabolites in human whole blood

PURPOSE

Synthetic cathinones, one of the largest groups of new psychoactive substances, represent a large analytical and interpretative challenge in forensic laboratories. Of these is the synthetic cathinones' instability in different biological samples, which may lead to drug concentration discrepancies when interpreting toxicological findings. In this study, the stability of a panel of synthetic cathinones and their dihydro-metabolites (n = 26) together with internal standard was monitored in human whole blood stored at various temperatures over 6 months. The influence of sodium fluoride as a preservative in blood collection tubes was also investigated.

METHODS

Samples were extracted using a two-step liquid-liquid extraction technique, and analyzed using a validated liquid chromatography-tandem mass spectrometry method following recommendations of published guidelines.

RESULTS

The influence of temperature over analytes' stability was an important element in whole blood samples, with - 40 °C being the best storage temperature for all tested analytes. Sodium fluoride did not significantly affect the stability of cathinones except at room temperature. Dihydro-metabolites displayed better stability in whole blood samples and remained detectable for a longer period of time under all tested conditions.

CONCLUSIONS

The data suggest that samples containing synthetic cathinones should be analyzed immediately, if possible. Alternatively, whole blood samples should be stored frozen (at - 40 °C or lower); however, (quantitative) results should be interpreted with caution after long-term storage. The data also promote the use of dihydro-metabolites as biomarkers for synthetic cathinones intake, as these reduced metabolites may be detected for longer period of time when compared with parent drugs in whole blood samples.

Determination of total cathinones with a single molecularly imprinted fluorescent sensor assisted by electromembrane microextraction

An electromembrane microextraction (EME)-assisted fluorescent molecularly imprinted polymer (MIP) sensing method is presented for detecting the total cathinone drugs in urine samples. In this detection system, the clean-up ability of EME eliminated the matrix effects on both target binding with MIPs and the luminescence of the fluorophore in the sensor. Moreover, by optimizing the extraction conditions of EME, different cathinone drugs with a same concentration show a same response on the single aggregation induced emission (AIE) based MIP (AIE-MIP) sensor (λ_ex = 360 nm, λ_em = 467 nm). The recoveries were 57.9% for cathinone (CAT) and 78.2% for methcathinone (MCAT). The EME-assisted "light-up" AIE-MIP sensing method displayed excellent performance with a linear range of 2.0-12.0 μmol L^-1 and a linear determination coefficient (R²) of 0.99. The limit of detection (LOD) value for EME-assisted "light-up" AIE-MIP sensing method was 0.3 μmol L^-1. The relative standard deviation (RSD) values for the detection were found to be within the range 2.0-12.0%. To the best of our knowledge, this is the first time that determination of total illicit drugs with a single fluorescent MIP sensor was achieved and also the first utilization of sample preparation to tune the sensing signal of the sensor to be reported. We believe that this versatile combination of fluorescent MIP sensor and sample preparation can be used as a common protocol for sensing the total amount of a group of analytes in various fields.

A Quantitative LC–MS/MS Method for the Detection of 16 Synthetic Cathinones and 10 Metabolites and Its Application to Suspicious Clinical and Forensic Urine Samples

Background: Synthetic cathinones currently represent one of the most predominant (sub)-classes of new psychoactive substance (NPS) in illicit drug markets. Despite the increased concerns caused by the constant introduction of new analogues, these drugs are not commonly assayed in routine drug testing procedures and may not be detected in standard screening procedures. This study presents a validated liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the detection and quantification of 16 synthetic cathinones and 10 metabolites in human urine. Methods: The method was validated for all analytes using published guidelines. The evaluated parameters achieved acceptable values according to the set criteria. Potential abuse of synthetic cathinones was investigated in suspicious urine samples from Saudi Arabia originating from workplace drug testing, pre-employment and Accident & Emergency (A&E). Such samples generated a presumptive positive immunoassay for amphetamine; however, they yielded a negative LC–MS/MS confirmation for this analyte, following the recommended cutoff values of Substance of Abuse and Mental Health Services Administration (SAMHSA) guidelines. Results: 5.8% of the analyzed samples were found to contain at least one target analyte, namely mephedrone and N-ethylpentylone, as well as their dihydro-metabolites. The results also revealed polydrug use with the synthetic cathinones being present together with other classical stimulant drugs. Conclusions: This is the first report of NPS use in Saudi Arabia with respect to designer stimulant drugs. Confirmatory urine analyses for suspicious stimulant use should extend beyond classical stimulants to cover a broad range of NPSs and their metabolites in order to report any otherwise potentially undetected/new analyte.

In Vitro Metabolic Study of Four Synthetic Cathinones: 4-MPD, 2-NMC, 4F-PHP and bk-EPDP

The use of illicit drugs is exceedingly prevalent in society, and several of them can be illegally purchased from the internet. This occurrence is particularly augmented by the rapid emergence of novel psychoactive substances (NPS), which are sold and distributed as “legal highs”. Amongst NPS, the class of synthetic cathinones represents stimulant substances exhibiting similar effects to amphetamine and its derivatives. Despite potentially being less psychoactive than amphetamine, synthetic cathinones are harmful substances for humans, and little or no information is available regarding their pharmacology and toxicology. The present study investigated the in vitro metabolism and metabolites of four recent synthetic cathinones, namely, 1-(4-methylphenyl)-2-(methylamino)-pentanone (4-MPD), 1-(4-methylphenyl)-2-dimethylamino-propanone (2-NMC), 1-(4-fluorophenyl)-2-(pyrrolidin-1-yl-hexanone (4F-PHP) and 1-(1,3-benzodioxol-5-yl)-2-(ethylamino)-1-pentanone (bk-EPDP). Our in vitro metabolism study resulted in 24 identified metabolites, including both phase I and phase II metabolites. All metabolites were detected and identified using liquid chromatography–high-resolution mass spectrometry and may serve as additional markers of abuse of these NPS in toxicological analyses.