Analytical characterization of "etonitazepyne," a new pyrrolidinyl-containing 2-benzylbenzimidazole opioid sold online

Drug Test Anal. 2021 Sep;13(9):1627-1634. doi: 10.1002/dta.3113. Epub 2021 Jun 19.


This paper reports on the identification and full chemical characterization of the substance colloquially called "etonitazepyne" or "N-pyrrolidino etonitazene" (2-(4-ethoxybenzyl)-5-nitro-1-(2-(pyrrolidin-1-yl)ethyl)-1H-benzo[d]imidazole), a potent NPS opioid of the 5-nitrobenzimidazole class. Identification of etonitazepyne was performed, on a sample purchased during routine monitoring of the drug market, using GC-MS, HRAM LC-MS/MS, 1 H NMR, and FTIR. The chromatographic data, together with the FTIR data, indicated the presence of a highly pure compound and already indicated a benzimidazole structure. The specific benzimidazole regio-isomer was confirmed using 1 H NMR spectroscopy, resulting in the unambiguous identification of etonitazepyne.

Keywords: benzimidazoles; etonitazene; new psychoactive substances; opioid NPS; pyrrolidine analogue.

MeSH terms

  • Analgesics, Opioid / analysis*
  • Analgesics, Opioid / chemistry
  • Benzimidazoles / analysis*
  • Benzimidazoles / chemistry
  • Chromatography, Liquid
  • Gas Chromatography-Mass Spectrometry
  • Illicit Drugs / analysis*
  • Illicit Drugs / chemistry
  • Magnetic Resonance Spectroscopy
  • Spectroscopy, Fourier Transform Infrared
  • Tandem Mass Spectrometry


  • Analgesics, Opioid
  • Benzimidazoles
  • Illicit Drugs
  • etonitazene