Metabolism of Synthetic Cathinones. In: Zawilska JB, editor. Synthetic Cathinones. Cham: Springer International Publishing; 2018. pp. 71-96. [DOI: 10.1007/978-3-319-78707-7_5]

Metabolic stability and metabolite profiling of emerging synthetic cathinones

Synthetic cathinones constitute the second largest groups of new psychoactive substances (NPS), which are especially popular among adolescents and young adults. Due to their potential toxicity, the recreational use of these NPS constitute a serious worldwide public health problem. However, their fast appearance in the market renders the continuous updating of NPS information highly challenging for forensic authorities. The unavailability of pharmacokinetic data for emerging NPS is critical for forensic and clinical verifications. With the ultimate goal of having a proactive approach towards the NPS issue, high resolution mass spectrometry was used in the current work to assess preliminary pharmacokinetic data for 8 selected cathinones: 4 reported substances (4-CIC, 3-CMC, 4-CMC and 4-MEAP) and 4 previously unreported ones (3-CIC, 4-MDMB, 4-MNEB and 4-MDMP) for which the emergence on the NSP market is expected to be eminent, were also included in this study. Based on the calculation of pharmacokinetic parameters, half-life and intrinsic clearance, 4-CMC and 4-MDMB are low and high clearance compounds, respectively, and all the remaining cathinones included in this study are intermediate clearance compounds. This fact anticipates the key role of metabolites as suitable biomarkers to extend detection windows beyond those provided by the parent cathinones. Reduction of the keto group and hydroxylation on the alkyl chains were the common metabolic pathways identified for all cathinones. However, the relative importance of these metabolic transformations is dependent on the cathinone substituents. The glucuronic acid conjugation to metabolites stemming for keto group reduction constituted the sole Phase II transformation identified. To our knowledge, this study constitutes the first metabolite profiling of the already reported synthetic cathinones 4-CIC, 3-CMC and 4-CMC. Noteworthy is the fact that 3-CMC accounts for almost a quarter of the quantity of powders seized during 2020. The analytical methods developed, and the metabolites characterized, are now available to be included in routine screening methods to attest the consumption of the 8 cathinones studied.

In vitro metabolic profile of mexedrone, a mephedrone analog, studied by high- and low-resolution mass spectrometry

Mexedrone is a synthetic cathinone structurally related to mephedrone, which belongs to the class of N‐alkyl cathinone derivatives, whose metabolic profile has not been fully clarified yet. This study considers the in vitro phase I metabolism of mexedrone, to pre‐select the most appropriate marker(s) of intake. Mexedrone was incubated in the presence of either human liver microsomes or single recombinant CYP450 isoforms. The metabolic profile was outlined by ultra‐high‐performance liquid chromatography coupled to both high‐ and low‐resolution mass spectrometry. In detail, the phase I metabolic profile of mexedrone was initially defined by a time‐of‐flight analyzer, while the chemical structures of the detected metabolites and the potential presence of minor metabolites were subsequently studied by tandem mass spectrometry, using a triple quadrupole analyzer. The main phase I metabolic reactions were hydroxylation and N‐ and O‐dealkylation. The CYP450 isoforms most involved were CYP2C19, responsible for the formation of both hydroxylated and dealkylated metabolites, followed by CYP2D6 and CYP1A2, involved in the hydroxylation reactions only. Finally, a significant fraction of mexedrone unchanged was also detected. Based on this evidence, the most appropriate markers of intake are mexedrone unchanged and the hydroxylated metabolites.

An updated review on synthetic cathinones

Cathinone, the main psychoactive compound found in the plant Catha edulis Forsk. (khat), is a β-keto analogue of amphetamine, sharing not only the phenethylamine structure, but also the amphetamine-like stimulant effects. Synthetic cathinones are derivatives of the naturally occurring cathinone that largely entered the recreational drug market at the end of 2000s. The former "legal status", impressive marketing strategies and their commercial availability, either in the so-called "smartshops" or via the Internet, prompted their large spread, contributing to their increasing popularity in the following years. As their popularity increased, the risks posed for public health became clear, with several reports of intoxications and deaths involving these substances appearing both in the social media and scientific literature. The regulatory measures introduced thereafter to halt these trending drugs of abuse have proved to be of low impact, as a continuous emergence of new non-controlled derivatives keep appearing to replace those prohibited. Users resort to synthetic cathinones due to their psychostimulant properties but are often unaware of the dangers they may incur when using these substances. Therefore, studies aimed at unveiling the pharmacological and toxicological properties of these substances are imperative, as they will provide increased expertise to the clinicians that face this problem on a daily basis. The present work provides a comprehensive review on history and legal status, chemistry, pharmacokinetics, pharmacodynamics, adverse effects and lethality in humans, as well as on the current knowledge of the neurotoxic mechanisms of synthetic cathinones.

Adverse outcome pathways induced by 3,4-dimethylmethcathinone and 4-methylmethcathinone in differentiated human SH-SY5Y neuronal cells

Cathinones (β-keto amphetamines), widely abused in recreational settings, have been shown similar or even worse toxicological profile than classical amphetamines. In the present study, the cytotoxicity of two β-keto amphetamines [3,4-dimethylmethcathinone (3,4-DMMC) and 4-methylmethcathinone (4-MMC)], was evaluated in differentiated dopaminergic SH-SY5Y cells in comparison to methamphetamine (METH). MTT reduction and NR uptake assays revealed that both cathinones and METH induced cytotoxicity in a concentration- and time-dependent manner. Pre-treatment with trolox (antioxidant) partially prevented the cytotoxicity induced by all tested drugs, while N-acetyl-L-cysteine (NAC; antioxidant and glutathione precursor) and GBR 12909 (dopamine transporter inhibitor) partially prevented the cytotoxicity induced by cathinones, as evaluated by the MTT reduction assay. Unlike METH, cathinones induced oxidative stress evidenced by the increase on intracellular levels of reactive oxygen species (ROS), and also by the decrease of intracellular glutathione levels. Trolox prevented, partially but significantly, the ROS generation elicited by cathinones, while NAC inhibited it completely. All tested drugs induced mitochondrial dysfunction, since they led to mitochondrial membrane depolarization and to intracellular ATP depletion. Activation of caspase-3, indicative of apoptosis, was seen both for cathinones and METH, and confirmed by annexin V and propidium iodide positive staining. Autophagy was also activated by all drugs tested. Pre-incubation with bafilomycin A1, an inhibitor of the vacuolar H⁺-ATPase, only protected against the cytotoxicity induced by METH, which indicates dissimilar toxicological pathways for the tested drugs. In conclusion, the mitochondrial impairment and oxidative stress observed for the tested cathinones may be key factors for their neurotoxicity, but different outcome pathways seem to be involved in the adverse effects, when compared to METH.

Synthetic cathinones: an evolving class of new psychoactive substances

Synthetic cathinones (SCat) are amphetamine-like psychostimulants that emerged onto drug markets as "legal" alternatives to illicit drugs such as ecstasy, cocaine, and amphetamines. Usually they are sold as "bath salts," "plant food," or "research chemicals," and rapidly gained popularity amongst drugs users due to their potency, low cost, and availability. In addition, internet drug sales have been replacing the old way of supplying drugs of abuse, contributing to their rapid spread. Despite the legislative efforts to control SCat, new derivatives continue to emerge on the recreational drugs market and their abuse still represents a serious public health issue. To date, about 150 SCat have been identified on the clandestine drugs market, which are one of the largest groups of new psychoactive substances (NPS) monitored by the United Nations Office on Drugs and Crime and the European Monitoring Center for Drugs and Drug Addiction. Similar to the classical stimulants, SCat affect the levels of catecholamines in the central nervous system, which results in their psychological, behavioral and toxic effects. Generally, the effects of SCat greatly differ from drug to drug and relatively little information is available about their pharmacology. The present work provides a review on the development of SCat as substances of abuse, current patterns of abuse and their legal status, chemical classification, known mechanisms of action, and their toxicological effects.

A review of the influence of functional group modifications to the core scaffold of synthetic cathinones on drug pharmacokinetics

RATIONALE

The synthetic cathinones are a class of designer drugs of abuse that share a common core scaffold. The pharmacokinetic profiles of the synthetic cathinones vary based on the substitutions to the core scaffold.

OBJECTIVES

To provide a summary of the literature regarding the pharmacokinetic characteristics of the synthetic cathinones, with a focus on the impact of the structural modifications to the pharmacokinetics.

RESULTS

In many, but not all, instances the pharmacokinetic characteristics of the synthetic cathinones can be reasonably predicted based on the substitutions to the core scaffold. Mephedrone and methylone are chemically alike and have similar T_max and t_1/2 in male rats. MDPV, a structurally distinct synthetic cathinone from mephedrone and methylone, has a lower T_max and t_1/2. Increasing the length of the alkyl chain on the α position of methylone, to produce pentylone, results in increased plasma concentrations and longer t_1/2. Metabolism of the synthetic cathinones is reasonably predictable based on the chemical structure, and several phase I metabolites retain pharmacodynamic activity. CYP2D6 is implicated in the metabolism of all of the synthetic cathinones, and other P450s (CYP1A2, CYP2B6, and CYP2C19) are known to contribute variably to the metabolism of specific synthetic cathinones.

CONCLUSIONS

Continued research will lead to a better understanding of the pharmacokinetic changes associated with structural modifications to the cathinone scaffold, and potentially in the long range, enhanced overdose and addiction therapy. Additionally, the areas of polydrug use and pharmacogenetics have been largely overlooked with regard to synthetic cathinones.