First identification, chemical analysis and pharmacological characterization of N-piperidinyl etonitazene (etonitazepipne), a recent addition to the 2-benzylbenzimidazole opioid subclass
Open accessAbstract
N-Piperidinyl etonitazene ('etonitazepipne') represents a recent addition to the rapidly expanding class of 2-benzylbenzimidazole 'nitazene' opioids. Following its first identification in an online-sourced powder and in biological samples from a patient seeking help for detoxification, this report details its in-depth chemical analysis and pharmacological characterization. Analysis of the powder via different techniques (LC-HRMS, GC-MS, UHPLC-DAD, FT-IR) led to the unequivocal identification of N-piperidinyl etonitazene. Furthermore, we report the first activity-based detection and analytical identification of N-piperidinyl etonitazene in authentic samples. LC-HRMS analysis revealed concentrations of 1.21 ng/mL in serum and 0.51 ng/mL in urine, whereas molecular networking enabled the tentative identification of various (potentially active) urinary metabolites. In addition, we determined that the extent of opioid activity present in the patient's serum was equivalent to the in vitro opioid activity exerted by 2.5-10 ng/mL fentanyl or 10-25 ng/mL hydromorphone in serum. Radioligand binding assays in rat brain tissue revealed that the drug binds with high affinity (K i = 14.3 nM) to the µ-opioid receptor (MOR). Using a MOR-β-arrestin2 activation assay, we found that N-piperidinyl etonitazene is highly potent (EC 50 = 2.49 nM) and efficacious (E max = 183% versus hydromorphone) in vitro. Pharmacodynamic evaluation in male Sprague Dawley rats showed that N-piperidinyl etonitazene induces opioid-like antinociceptive, cataleptic, and thermic effects, its potency in the hot plate assay (ED 50 = 0.0205 mg/kg) being comparable to that of fentanyl (ED 50 = 0.0209 mg/kg), and > 190 times higher than that of morphine (ED 50 = 3.940 mg/kg). Taken together, our findings indicate that N-piperidinyl etonitazene is a potent opioid with the potential to cause harm in users.
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Some nitazene analogs are more potent than fentanyl.
“Importantly, some analytes included in the nitazene class are reported to be more potent than fentanyl, posing a greater risk to drug users while potentially increasing analytical challenges in the laboratory, particularly for screening due to the need for low limits of detection [14][15][16][17][18].”
From Evaluation of enzyme-linked immunosorbent assay screening kits for the detection of nitazene analogs (2025) · cites this paper as [15]
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- Authors
- Vandeputte, M. M., Verougstraete, N., Walther, D., Glatfelter, G. C., Malfliet, J., Baumann, M. H., Verstraete, A. G., & Stove, C. P.
- Affiliations
- Ghent University (BE)
- Ghent University Hospital (BE)
- National Institutes of Health (US)
- Corresponding author
- Stove, Christophe P.
- ORCID
- Venue
- Archives of Toxicology
- Published
- 2022-04-21
- Volume
- 96
- Issue
- 6
- Pages
- 1865-1880
- ISSN
- 0340-5761 (ISSN-L)
- 1432-0738
- PMC
- PMC12908708
- OpenAlex
- W4224302202
- Cited by
- 44
- References
- 38
- Citations by year
- 2026: 7 · 2025: 12 · 2024: 15 · 2023: 6 · 2022: 4
- FWCI
- 6.17
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Archives of Toxicology (publishedVersion)
- PubMed (publishedVersion)
- PubMed Central (publishedVersion)
- Ghent University Academic Bibliography (Ghent University) (submittedVersion, other-oa)
- Funders
- Fonds Wetenschappelijk Onderzoek (1S81522N, 1703320N, G069419N)
- Bijzonder Onderzoeksfonds (01J15517)
- National Institute on Drug Abuse
- Topics
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Toxicology › Forensic Toxicology and Drug Analysis
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Opioid Use Disorder Treatment
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Alkaloids: synthesis and pharmacology
- Keywords
- opioid pharmacology, antinociception, catalepsy, urinary metabolites, molecular networking
- MeSH terms
- Analgesics, Opioid, Animals, Benzimidazoles, Hydromorphone, Fentanyl, Humans, Male, Powders, Rats, Sprague-Dawley, Spectroscopy, Fourier Transform Infrared, Rats
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