Synthesis, characterization, and monoamine transporter activity of the new psychoactive substance 3',4'-methylenedioxy-4-methylaminorex (MDMAR)

Genotoxicological Characterization of (±)cis-4,4'-DMAR and (±)trans-4,4'-DMAR and Their Association

The novel psychoactive substance (NPS) 4-Methyl-5-(4-methylphenyl)-4,5-dihydroxazol-2-amine (4,4′-DMAR) shows psychostimulant activity. Data on the acute toxicity of 4,4′-DMAR are becoming increasingly available, yet the long-term effects are still almost unknown. In particular, no data on genotoxicity are available. Therefore, the aim of the present study was to evaluate its genotoxic potential using the “In Vitro Mammalian Cell Micronucleus Test” (MNvit) on (±)cis-4,4′-DMAR and (±)trans-4,4′-DMAR and their associations. The analyses were conducted in vitro on human TK6 cells. To select suitable concentrations for MNvit, we preliminarily evaluated cytotoxicity and apoptosis. All endpoints were analysed by flow cytometry. The results reveal the two racemates’ opposite behaviours: (±)cis-4,4′-DMAR shows a statistically significant increase in micronuclei (MNi) frequency that (±)trans-4,4′-DMAR is completely incapable of. This contrast confirms the well-known possibility of observing opposite biological effects of the cis- and trans- isomers of a compound, and it highlights the importance of testing single NPSs that show even small differences in structure or conformation. The genotoxic capacity demonstrated stresses an additional alarming toxicological concern related to this NPS. Moreover, the co-treatments indicate that consuming both racemates will magnify the genotoxic effect, an aspect to consider given the unpredictability of illicit drug composition.

Worsening of the Toxic Effects of (±)Cis-4,4'-DMAR Following Its Co-Administration with (±)Trans-4,4'-DMAR: Neuro-Behavioural, Physiological, Immunohistochemical and Metabolic Studies in Mice

4,4’-Dimethylaminorex (4,4’-DMAR) is a new synthetic stimulant, and only a little information has been made available so far regarding its pharmaco-toxicological effects. The aim of this study was to investigate the effects of the systemic administration of both the single (±)cis (0.1–60 mg/kg) and (±)trans (30 and 60 mg/kg) stereoisomers and their co-administration (e.g., (±)cis at 1, 10 or 60 mg/kg + (±)trans at 30 mg/kg) in mice. Moreover, we investigated the effect of 4,4′-DMAR on the expression of markers of oxidative/nitrosative stress (8-OHdG, iNOS, NT and NOX2), apoptosis (Smac/DIABLO and NF-κB), and heat shock proteins (HSP27, HSP70, HSP90) in the cerebral cortex. Our study demonstrated that the (±)cis stereoisomer dose-dependently induced psychomotor agitation, sweating, salivation, hyperthermia, stimulated aggression, convulsions and death. Conversely, the (±)trans stereoisomer was ineffective whilst the stereoisomers’ co-administration resulted in a worsening of the toxic (±)cis stereoisomer effects. This trend of responses was confirmed by immunohistochemical analysis on the cortex. Finally, we investigated the potentially toxic effects of stereoisomer co-administration by studying urinary excretion. The excretion study showed that the (±)trans stereoisomer reduced the metabolism of the (±)cis form and increased its amount in the urine, possibly reflecting its increased plasma levels and, therefore, the worsening of its toxicity.

The psychoactive aminoalkylbenzofuran derivatives, 5-APB and 6-APB, mimic the effects of 3,4-methylenedioxyamphetamine (MDA) on monoamine transmission in male rats

RATIONALE

The nonmedical use of new psychoactive substances (NPS) is a worldwide public health concern. The so-called "benzofury" compounds, 5-(2-aminopropyl)benzofuran (5-APB) and 6-(2-aminopropyl)benzofuran (6-APB), are NPS with stimulant-like properties in human users. These substances are known to interact with monoamine transporters and 5-HT receptors in transfected cells, but less is known about their effects in animal models.

METHODS

Here, we used in vitro monoamine transporter assays in rat brain synaptosomes to characterize the effects of 5-APB and 6-APB, together with their N-methyl derivatives 5-MAPB and 6-MAPB, in comparison with 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA). In vivo neurochemical and behavioral effects of 5-APB (0.3 and 1.0 mg/kg, i.v.) and 6-APB (0.3 and 1.0 mg/kg, i.v.) were assessed in comparison with MDA (1.0 and 3.0 mg/kg, i.v.) using microdialysis sampling in the nucleus accumbens of conscious male rats.

RESULTS

All four benzofuran derivatives were substrate-type releasers at dopamine transporters (DAT), norepinephrine transporters (NET), and serotonin transporters (SERT) with nanomolar potencies, similar to the profile of effects produced by MDA and MDMA. However, the benzofurans were at least threefold more potent than MDA and MDMA at evoking transporter-mediated release. Like MDA, both benzofurans induced dose-related elevations in extracellular dopamine and serotonin in the brain, but benzofurans were more potent than MDA. The benzofuran derivatives also induced profound behavioral activation characterized by forward locomotion which lasted for at least 2 h post-injection.

CONCLUSIONS

Overall, benzofurans are more potent than MDA in vitro and in vivo, producing sustained stimulant-like effects in rats. These data suggest that benzofuran-type compounds may have abuse liability and could pose risks for adverse effects, especially if used in conjunction with abused drugs or medications which enhance monoamine transmission in the brain.

Designer drugs: mechanism of action and adverse effects

Psychoactive substances with chemical structures or pharmacological profiles that are similar to traditional drugs of abuse continue to emerge on the recreational drug market. Internet vendors may at least temporarily sell these so-called designer drugs without adhering to legal statutes or facing legal consequences. Overall, the mechanism of action and adverse effects of designer drugs are similar to traditional drugs of abuse. Stimulants, such as amphetamines and cathinones, primarily interact with monoamine transporters and mostly induce sympathomimetic adverse effects. Agonism at μ-opioid receptors and γ-aminobutyric acid-A (GABA_A) or GABA_B receptors mediates the pharmacological effects of sedatives, which may induce cardiorespiratory depression. Dissociative designer drugs primarily act as N-methyl-d-aspartate receptor antagonists and pose similar health risks as the medically approved dissociative anesthetic ketamine. The cannabinoid type 1 (CB₁) receptor is thought to drive the psychoactive effects of synthetic cannabinoids, which are associated with a less desirable effect profile and more severe adverse effects compared with cannabis. Serotonergic 5-hydroxytryptamine-2A (5-HT_2A) receptors mediate alterations of perception and cognition that are induced by serotonergic psychedelics. Because of their novelty, designer drugs may remain undetected by routine drug screening, thus hampering evaluations of adverse effects. Intoxication reports suggest that several designer drugs are used concurrently, posing a high risk for severe adverse effects and even death.

Characterization of a recently detected halogenated aminorex derivative: para-fluoro-4-methylaminorex (4'F-4-MAR)

Despite the fact that 33% of the new psychoactive substances seized in 2015 were synthetic cathinones, the number of these derivatives has been decreasing in the last years, probably as a consequence of the unfavourable effects reported by users. Thus, the list of possible cathinone analogues is expected to get shorter, and it is likely that the same moiety changes applied for the preparation of synthetic cathinones will be applied in the near future to other stimulants in the search for favourable alternatives to controlled substances. This is evidenced by the increase in newly reported substances belonging to stimulant classes other than cathinones. One of the possible candidates for a new backbone from which to base new stimulants is aminorex, which is classified as a Schedule I substance by the Drug Enforcement Administration. Three derivatives have been reported until now: 4-methylaminorex or 4-MAR (also categorized as a Schedule I substance), para-methyl-4-methylaminorex (4,4′-DMAR) and 3′,4′-methylenedioxy-4-methylaminorex (MDMAR). Recently, the new halogenated 4-MAR derivative, para-fluoro-4-methylaminorex, characterised in this work (and abbreviated as pF-4-methylaminorex or 4′F-4-MAR) was detected by the Slovenian police. In the present work, 4′F-4-MAR has been characterized by high resolution mass spectrometry and nuclear magnetic resonance in a sample obtained from an anonymous consumer. This research shows that the same modifications applied for the preparation of synthetic cathinones are being used to prepare new stimulants based on the aminorex backbone.

DARK Classics in Chemical Neuroscience: Aminorex Analogues

Aminorex (5-phenyl-4,5-dihydro-1,3-oxazol-2-amine) and 4-methylaminorex (4-methyl-5-phenyl-4,5-dihydro-1,3-oxazol-2-amine) are psychostimulants that have long been listed in Schedules IV and I of the UN Convention on Psychotropic Substances of 1971. However, a range of psychoactive analogues exist that are not internationally controlled and therefore often classified as new psychoactive substances (NPS). Aminorex analogues encompass failed pharmaceuticals that reemerged as drugs of abuse, and newly synthesized substances that were solely designed for recreational use by clandestine chemists. NPS, sometimes also referred to as "designer drugs" in alignment with a phenomenon arising in the early 1980s, serve as alternatives to controlled drugs. Aminorex and its derivatives interact with monoaminergic neurotransmission by interfering with the function of monoamine transporters. Hence, these compounds share pharmacological and neurochemical similarities with amphetamines and cocaine. The consumption of aminorex, 4-methylaminorex and 4,4'-dimethylaminorex (4-methyl-5-(4-methylphenyl)-4,5-dihydro-1,3-oxazol-2-amine) has been associated with adverse events including death, bestowing an inglorious fame on aminorex-derived drugs. In this Review, a historical background is presented, as well as an account of the pharmacodynamic and pharmacokinetic properties of aminorex and various analogues. Light is shed on their misuse as drug adulterants of well-established drugs on the market. This Review not only provides a detailed overview of an abused substance-class, but also emphasizes the darkest aspect of the NPS market, i.e., deleterious side effects that arise from the ingestion of certain NPS, as knowledge of the pharmacology, the potency, or the identity of the active ingredients remains obscure to NPS users.

The psychostimulant (±)-cis-4,4'-dimethylaminorex (4,4'-DMAR) interacts with human plasmalemmal and vesicular monoamine transporters

(±)-cis-4,4'-Dimethylaminorex (4,4'-DMAR) is a new psychoactive substance (NPS) that has been associated with 31 fatalities and other adverse events in Europe between June 2013 and February 2014. We used in vitro uptake inhibition and transporter release assays to determine the effects of 4,4'-DMAR on human high-affinity transporters for dopamine (DAT), norepinephrine (NET) and serotonin (SERT). In addition, we assessed its binding affinities to monoamine receptors and transporters. Furthermore, we investigated the interaction of 4,4'-DMAR with the vesicular monoamine transporter 2 (VMAT2) in rat phaeochromocytoma (PC12) cells and synaptic vesicles prepared from human striatum. 4,4'-DMAR inhibited uptake mediated by human DAT, NET or SERT, respectively in the low micromolar range (IC₅₀ values < 2 μM). Release assays identified 4,4'-DMAR as a substrate type releaser, capable of inducing transporter-mediated reverse transport via DAT, NET and SERT. Furthermore, 4,4'-DMAR inhibited both the rat and human isoforms of VMAT2 at a potency similar to 3,4-methylenedioxymethylamphetamine (MDMA). This study identified 4,4'-DMAR as a potent non-selective monoamine releasing agent. In contrast to the known effects of aminorex and 4-methylaminorex, 4,4'-DMAR exerts profound effects on human SERT. The latter finding is consistent with the idea that fatalities associated with its abuse may be linked to monoaminergic toxicity including serotonin syndrome. The activity at VMAT2 suggests that chronic abuse of 4,4'-DMAR may result in long-term neurotoxicity.

4,4'-Dimethylaminorex ("4,4'-DMAR"; "Serotoni") misuse: A Web-based study

BACKGROUND

4,4'-DMAR (4,4'-dimethylaminorex; "Serotoni") is a potent stimulant drug that has recently been associated with a number of fatalities in Europe. Over the last few years, online communities have emerged as important resources for disseminating levels of technical knowledge on novel psychoactive substances.

OBJECTIVE

Analysing the information provided by the fora communities on 4,4'-DMAR use, additionally critical reviewing the available evidence-based literature on this topic.

METHODS

Different website drug fora were identified. A critical review of the existing evidence-based literature was undertaken. Individuation and analysis of qualitative data from the identified website fora were performed.

RESULTS

The combined search results identified six website fora from which a range of qualitative data on recurring themes was collected. These themes included routes of administration and doses; desired effects; adverse effects; comparison with other drugs; association with other drugs; medications self-administered to reverse 4,4'-DMAR action; overall impression; and provision of harm-reduction advice.

CONCLUSIONS

Although being characterized by a number of methodological limitations, the social networks' Web monitoring approach (netnography) may be helpful to better understand some of the clinical and psychopharmacological issues pertaining to a range of novel psychoactive substances, including 4,4'-DMAR, for which only extremely little, if any, scientific knowledge is available.

Brain Disposition of cis-para-Methyl-4-Methylaminorex (cis-4,4'-DMAR) and Its Potential Metabolites after Acute and Chronic Treatment in Rats: Correlation with Central Behavioral Effects

para-Methyl-4-methylaminorex (4,4'-DMAR) is a phenethylamine derivative with psychostimulant activity whose abuse has been associated with several deaths and a wide range of adverse effects. We recently validated a high-performance liquid chromatography-tandem mass spectrometry method to measure the compound's concentrations in plasma, and we applied it to describe the pharmacokinetic properties of 4,4'-DMAR after a single dose in rats. In this study, we investigated the brain disposition and metabolism of cis-4,4'-DMAR after intraperitoneal injection as well as its central behavioral effects. Locomotor activity increased after a single injection of 10 mg/kg, peaking at 2 hours and disappearing at 5 hours; in these conditions, brain absorption was very rapid, (t_max = 30-60 minutes) and large (brain-to-plasma ratio = 24); the half-life was approximately 50 minutes. After 14 daily doses, the compound's effect on locomotor activity was greater (approximately 20% compared with the effect after the first dose), but not for pharmacokinetic reasons. Using high-resolution mass spectrometry, we also identified four metabolites of cis-4,4'-DMAR in the plasma and brain of treated rats. Semiquantitative analysis indicated low brain permeability and very low brain concentrations, suggesting that these metabolites do not contribute to central behavioral effects; however, the metabolite originating from oxidation of the para-methyl group (M2) persisted in the plasma longer and at higher concentrations than the parent molecule and could be used to evaluate drug intake in human consumers. Finally, we describe the rewarding effect of cis-4,4'-DMAR in the conditioning place preference test, suggesting a high risk of addiction in humans.

New psychoactive substances: an overview on recent publications on their toxicodynamics and toxicokinetics

This review article covers English-written and PubMed-listed review articles and original studies published between January 2015 and April 2016 dealing with the toxicodynamics and toxicokinetics of new psychoactive substances. Compounds covered include stimulants and entactogens, synthetic cannabinoids, tryptamines, NBOMes, phencyclidine-like drugs, benzodiazepines, and opioids. First, an overview and discussion is provided on timely review articles followed by an overview and discussion on recent original studies. Both sections are then concluded by an opinion on these latest developments. This review shows that the NPS market is still highly dynamic and that the data published on their toxicodynamics and toxicokinetics can hardly keep pace with the appearance of new entities. However, data available are very helpful to understand and predict how NPS may behave in severe intoxication. The currently best-documented parameter is the in vitro metabolism of NPS, a prerequisite to allow detection of NPS in biological matrices in cases of acute intoxications or chronic consumption. However, additional data such as their chronic toxicity are still lacking.

Test purchase, synthesis and characterization of 3-fluorophenmetrazine (3-FPM) and differentiation from its ortho- and para-substituted isomers

The knowledge captured in patent and scientific research literature stimulates new ideas and fosters new drug development efforts. Manufacturers and entrepreneurs dedicated to the sale of 'research chemicals' and/or new psychoactive substances (NPS) also make use of access to information to identify, prepare, and launch a range of new substances. One of the most recent compounds to appear on the NPS market is the phenmetrazine analog 3-fluorophenmetrazine (3-FPM) which represents one of many phenylmorpholines designed to explore treatment options in areas such as obesity and drug dependence. The anorectic drug analogs phenmetrazine and phendimetrazine, used as prescription medicines before they were withdrawn, feature amphetamine-like properties associated with monoamine release. Available data on 3-FPM suggest that the effects might show mechanistic overlaps. This study describes the synthesis and extensive analytical characterization of 3-FPM and its differentiation from synthesized ortho- and para- substituted isomers, 2-FPM and 4-FPM, respectively. This study was triggered by the purchase of five powdered samples advertised as 3-FPM by five different Internet vendors based in the United Kingdom. The analytical data obtained for the vendor samples were consistent with the synthesized 3-FPM standard and differentiation between all three isomers was possible. The presence of positional isomers and the absence of suitable reference material can cause difficulties in the day-to-day operation of forensic work and given the rate at which many of the newly emerging NPS appear on the market, a comprehensive approach is needed when attempting to decipher the identity of NPS arriving onto the drug market. Copyright © 2016 John Wiley & Sons, Ltd.

Next generation of novel psychoactive substances on the horizon - A complex problem to face

BACKGROUND

The last decade has seen a rapid and continuous growth in the availability and use of novel psychoactive substances (NPS) across the world. Although various products are labeled with warnings "not for human consumption", they are intended to mimic psychoactive effects of illicit drugs of abuse. Once some compounds become regulated, new analogues appear in order to satisfy consumers' demands and at the same time to avoid criminalization. This review presents updated information on the second generation of NPS, introduced as replacements of the already banned substances from this class, focusing on their pharmacological properties and metabolism, routes of administration, and effects in humans.

METHODS

Literature search, covering years 2013-2015, was performed using the following keywords alone or in combination: "novel psychoactive substances", "cathinones", "synthetic cannabinoids", "benzofurans", "phenethylamines", "2C-drugs", "NBOMe", "methoxetamine", "opioids", "toxicity", and "metabolism".

RESULTS

More than 400 NPS have been reported in Europe, with 255 detected in 2012-2014. The most popular are synthetic cannabimimetics and psychostimulant cathinones; use of psychedelics and opioids is less common. Accumulating experimental and clinical data indicate that potential harms associated with the use of second generation NPS could be even more serious than those described for the already banned drugs.

CONCLUSIONS

NPS are constantly emerging on the illicit drug market and represent an important health problem. A significant amount of research is needed in order to fully quantify both the short and long term effects of the second generation NPS, and their interaction with other drugs of abuse.

4,4'-DMAR: chemistry, pharmacology and toxicology of a new synthetic stimulant of abuse

In recent years, the spread of new psychoactive substances has dramatically increased in term of availability of both number of compounds and chemical families. In November 2012, 4,4'-Dimethylaminorex (4,4'-DMAR), a novel synthetic stimulant, was first detected in the Netherlands. Between June 2013 and June 2014, thirty-one deaths associated with the consumption of this new drug have been registered across Europe. In this MiniReview, we have summarized the chemical, pharmacological and toxicological information about this new legal high.