Metabolic profile of the synthetic drug 4,4′-dimethylaminorex in urine by LC–MS-based techniques: selection of the most suitable markers of its intake

Abstract

Purpose In this study, the phase I and II metabolic pathways of 4,4′-dimethylaminorex were characterized to select the marker(s) of intake allowing the unequivocal identification of this novel psychoactive substance in urine samples. Methods The metabolic profile of 4,4′-dimethylaminorex was characterized using both in vitro and in vivo models. In detail, for the in vitro experiments, either pooled human liver microsomes or recombinant cytochrome P450 isoforms were selected, whereas the in vivo investigation was performed on male mice ICR (CD-1®). Sample preparation included enzymatic hydrolysis followed by liquid/liquid extraction. The instrumental analysis was performed by ultra-high-performance liquid chromatography coupled to either high- or low-resolution tandem mass spectrometry. Results Five metabolic products were isolated only for the cis-isomer: the phase I metabolic reactions included hydrolysis, carboxylation, hydroxylation, and carbonylation. CYP2D6 was the principal isoenzyme involved, and the incubation in the presence of different allelic variants showed significant alteration on the metabolic profile. Once formed, the phase I metabolites underwent extensive conjugation. Not only the most abundant compounds detected, but also those with the most extended window of detection, were the carboxylated and the hydroxylated metabolites. These analytes together with the parent compound were selected as the most suitable markers of intake. Conclusions Knowledge of the metabolic profiles of the new drugs is essential for their fast identification. Phase I and phase II metabolites of 4,4′-dimethylaminorex were identified and selected as markers of intake, to be considered as the most suitable analytical targets in forensic toxicology.

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

“…At present, no in vivo pharmacological studies have been performed with the (±)trans-4,4 -DMAR stereoisomer whilst only one in vitro pharmacodynamic study has been published showing that (±)trans-4,4 -DMAR is a substrate-type releaser at the DAT, NET transporters and a SERT uptake blocker in rat brain tissue with a lower potency than the (±)cis-4,4 -DMAR stereoisomer [14]. However, in a recent pharmacokinetic study it was found that whilst the (±)cis-4,4 -DMAR compound is metabolised and excreted in the mouse urine, the (±)trans-4,4 -DMAR stereoisomer is not metabolised [84] suggesting a stereoselective metabolism and disposition of 4,4 -DMAR. This is common in stereoisomers of a drug that generally metabolised with different metabolic profile [85] both in pharmaceutical [86] and in abusing drugs [87,88].…”

“…Urine samples were treated and analysed through a protocol already used by our group for the analysis of the excretion of stimulant drugs in mice [84,112]. Briefly, our protocol allowed the conversion of conjugated metabolites (i.e., sulfo-and glucorono-conjugates) to phase I metabolites after two hydrolysis steps.…”

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

“…This study aimed to define the phase I biotransformation pathways of mexedrone. For this purpose, due to the strict regulations for conducting controlled administration studies in humans and animals, we have followed the same experimental strategy already followed in similar studies, [36][37][38][39][40] focusing our attention on the in vitro metabolic profile of mexedrone, studied using human liver microsomes and isolated CYP450 recombinant isoforms.…”

Prescription Drug Misuse in “Clubbers” and Disco Goers in Ibiza

“…An Agilent 1290 Infinity II UHPLC with a binary gradient system and an automatic injector (Agilent Technologies, Cernusco sul Naviglio, Milano, Italy) was used for the chromatographic separation. The instrument was equipped with an Agilent ZORBAX Eclipse Plus C18 column (100 × 2.1 mm i.d., particle size 1.8 μm) ( 37 ). The detector was an Orbitrap Q Exactive (Thermo Fisher Scientific) with an ESI source.…”