Urinary excretion profile of methiopropamine in mice following intraperitoneal administration: A liquid chromatography–tandem mass spectrometry investigation

Abstract

We have considered the urinary excretion profile of methiopropamine (MPA), a thiophene ring-based structural analog of methamphetamine with similar stimulant effects, with the aim of selecting the most appropriate marker(s) of intake that may be useful in forensic analysis. For this purpose, in vitro studies were preliminarily performed on human liver microsomes for tracing the phase I metabolic pathways of MPA, preselecting the best candidates as potential target analytes, and designing the optimal experimental strategy. In vivo studies were then conducted on mice, after the intraperitoneal administration of a 10-mg/kg dose. Urine samples were collected every 3 h in the first 9 h and, subsequently, from 24 to 36 h, and stored at-80 C until further analysis. The measurements were performed using a targeted procedure based on liquid/liquid extraction followed by liquid chromatography-tandem mass spectrometry analysis. Our results show that in the time interval 0-9 h after administration, MPA was extensively oxidized mainly to nor-MPA, oxo-MPA, and two hydroxylated metabolites (ie, hydroxy-aryl-methiopropamine and hydroxy-alkylmethiopropamine). All phase I metabolites underwent phase II metabolism, with the formation of nor-hydroxy-methiopropamine only in phase II, confirmed by the results obtained after enzymatic hydrolysis with β-glucuronidase and arylsulfatase. In the time interval 24-36 h after administration, only unchanged MPA and nor-MPA were detected, suggesting that these two markers are those endowed with the highest diagnostic value. The method was validated for these two principal markers, proving to be fit for anti-doping, toxicological, and forensic analyses.

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

“…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.…”

Comparative Neuropharmacology and Pharmacokinetics of Methamphetamine and Its Thiophene Analog Methiopropamine in Rodents

“…We found that the nor-metabolite was present at a maximum concentration 24× and 15× lower than the concentration of methiopropamine in the blood and brain, respectively. A recent study examining the urine excretion profile of methiopropamine after administration in mice reported the presence of nor-methiopropamine, oxo-methiopropamine and two hydroxylated metabolites in addition to the unchanged drug [ 16 ]. However, only methiopropamine and nor-methiopropamine were detected for a longer time period after exposure, and the authors concluded that these two analytes had the highest diagnostic value in toxicological analysis.…”

“…As a comparison, recreational users driving under the influence of drugs displayed a mean methiopropamine concentration of 0.018 µg/mL (0.12 µM) in the blood [ 5 ], whereas a fatal intoxication case reported 38 µg/mL (245 µM) [ 14 ]. Camuto et al [ 16 ] estimated a dose of 10 mg/kg in mice to be equivalent to a normal-to-high recreational human dose (~48 mg).…”

Annual banned‐substance review: Analytical approaches in human sports drug testing 2019/2020

“…In some instances, AAFs with stimulants such as methylenedioxymethamphetamine (MDMA) were eventually found to originate from an act of sabotage as reviewed in a chronicle by Baltazar‐Martins et al 156 ; however, there is also an ever‐growing pool of new additions to the list of new psychoactive substances (NPS, presumably designed to escape detection), some of which necessitate consideration in sports drug testing. The elimination profile of methiopropamine (Figure 1, 3 ) was studied in a mouse model by Camuto et al, demonstrating the urinary presence of the intact drug as well as dealkylated, oxidized, and hydroxylated analogs and corresponding phase‐II metabolites 157 . Following an intraperitoneal administration of a 10 mg/kg dose, urine specimens were sampled up to 36 hr and subjected to an LC‐MS/MS‐based analysis for unconjugated and conjugated biotransformation products.…”