2-methiopropamine, a thiophene analogue of methamphetamine: studies on its metabolism and detectability in the rat and human using GC-MS and LC-(HR)-MS techniques

Anal Bioanal Chem. 2013 Apr;405(10):3125-35. doi: 10.1007/s00216-013-6741-4. Epub 2013 Jan 30.

Abstract

2-Methiopropamine [1-(thiophen-2-yl)-2-methylaminopropane, 2-MPA], a thiophene analogue of methamphetamine, is available from online vendors selling "research chemicals." The first samples were seized by the German police in 2011. As it is a recreational stimulant, its inclusion in routine drug screening protocols should be required. The aims of this study were to identify the phase I and II metabolites of 2-MPA in rat and human urine and to identify the human cytochrome-P450 (CYP) isoenzymes involved in its phase I metabolism. In addition, the detectability of 2-MPA in urine samples using the authors' well-established gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-linear ion trap-mass spectrometry (LC-MS(n)) screening protocols was also evaluated. The metabolites were isolated from rat and human urine samples by solid-phase extraction without or following enzymatic cleavage of conjugates. The phase I metabolites, following acetylation, were separated and identified by GC-MS and/or liquid chromatography-high-resolution linear ion trap mass spectrometry (LC-HR-MS(n)) and the phase II metabolites by LC-HR-MS(n). The following major metabolic pathways were proposed: N-demethylation, hydroxylation at the side chain and at the thiophene ring, and combination of these transformations followed by glucuronidation and/or sulfation. CYP1A2, CYP2C19, CYP2D6, and CYP3A4 were identified as the major phase I metabolizing enzymes. They were also involved in the N-demethylation of the analogue methamphetamine and CYP2C19, CYP2D6, and CYP3A4 in its ring hydroxylation. Following the administration of a typical user's dose, 2-MPA and its metabolites were identified in rat urine using the authors' GC-MS and the LC-MS(n) screening approaches. Ingestion of 2-MPA could also be detected by both protocols in an authentic human urine sample.

Publication types

  • Evaluation Study

MeSH terms

  • Animals
  • Chromatography, Liquid / methods*
  • Cytochrome P-450 Enzyme System / metabolism
  • Gas Chromatography-Mass Spectrometry / methods*
  • Humans
  • Male
  • Methamphetamine / analogs & derivatives
  • Methamphetamine / metabolism
  • Methamphetamine / urine*
  • Rats
  • Rats, Wistar
  • Thiophenes / chemistry
  • Thiophenes / metabolism
  • Thiophenes / urine*

Substances

  • Thiophenes
  • Methamphetamine
  • Cytochrome P-450 Enzyme System