June 17, 2021
New High Potency Synthetic Opioid N-Pyrrolidino Etonitazene (Etonitazepyne) Linked to Overdoses Across United States
N-Pyrrolidino etonitazene (etonitazepyne) is a new high potency synthetic opioid bearing structural resemblance to etonitazene, a synthetic opioid that is nationally and internationally controlled. N-Pyrrolidino etonitazene is dissimilar in structure to other synthetic opioids typically encountered in forensic casework (e.g., fentanyl). Unlike the 2-benzylbenzimidazole analogues that were first synthesized and reported in the literature in the 1950s (e.g., metonitazene, isotonitazene), N-pyrrolidino etonitazene does not appear in prior literature or patents. Recent in vitro pharmacological data suggest that this new opioid exhibits potency similar to etonitazene (~20x more potent than fentanyl). N-Pyrrolidino etonitazene was first reported by NPS Discovery in May 2021 following initial detection in a toxicology case. To date, eight blood specimens associated with postmortem death investigations in the U.S. have contained N-pyrrolidino etonitazene; additional confirmations are pending. The toxicity of N-pyrrolidino etonitazene has not been examined or reported but recent association with death among people who use drugs leads professionals to believe this synthetic opioid retains the potential to cause widespread harm and is of public health concern. Identifications of N-pyrrolidino etonitazene have also been reported recently from agencies in Europe.