Etonitazepyne (IUPAC name: 2-[(4-ethoxyphenyl)methyl]-5-nitro-1-(2-pyrrolidin-1-ylethyl)-1H-benzoimidazole, also known as N-pyrrolidino etonitazene) is a benzimidazole-derived synthetic opioid with a chemical structure and pharmacological similarities to Schedule I drugs (under the 1961 United Nations Conventions) such as etonitazene. Etonitazepyne appears to be an analog of benzylbenzimidazole derivatives with analgesic properties that were initially synthesized in the late 1950s, although it was not described in that series.
The reported effects after etonitazepyne use include euphoria, drowsiness, itchiness, nausea and/or vomiting, sweating and difficulty in breathing.