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. Author manuscript; available in PMC: 2026 Feb 17.
Published in final edited form as: Arch Toxicol. 2022 Apr 21;96(6):1865–1880. doi: 10.1007/s00204-022-03294-2

Table 2.

Overview of potency (EC50) and efficacy (Emax, relative to hydromorphone) values as obtained in the MOR activation assay. 95% confidence intervals are indicated between brackets.

EC50 (nM) Emax (% of hydromorphone)
N-piperidinyl etonitazene reference standard 2.49 (1.67–3.74) 183 (173–194)
N-piperidinyl etonitazene sourced powder 3.06 (2.19–4.26) 180 (172–189)
Morphine 134 (80.8–228) 103 (96.2–109)
Fentanyl 16.8 (11.7–24.4) 147 (139–155)
Etonitazene 0.370 (0.232–0.585) 182 (171–193)
Hydromorphone 23.2 (16.8–32.4) 99.9 (95.1–105)