{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,2]],"date-time":"2026-05-02T10:48:25Z","timestamp":1777718905890,"version":"3.51.4"},"reference-count":25,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2023,7,21]],"date-time":"2023-07-21T00:00:00Z","timestamp":1689897600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100003130","name":"Fonds Wetenschappelijk Onderzoek","doi-asserted-by":"publisher","award":["1S81522N"],"award-info":[{"award-number":["1S81522N"]}],"id":[{"id":"10.13039\/501100003130","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003130","name":"Fonds Wetenschappelijk Onderzoek","doi-asserted-by":"publisher","award":["G069419N"],"award-info":[{"award-number":["G069419N"]}],"id":[{"id":"10.13039\/501100003130","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["analyticalsciencejournals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Drug Testing and Analysis"],"published-print":{"date-parts":[[2024,3]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>New synthetic opioids (NSOs) with diverse chemical structures continue to appear on recreational drug markets worldwide. U\u2010type opioids have become one of the largest groups of non\u2010fentanyl\u2010related NSOs. Starting in 2020, a previously unreported U\u2010compound coined \u201c\u03b2\u2010U10\u201d (2\u2010naphthyl U\u201047700; <jats:italic>N<\/jats:italic>\u2010[2\u2010(dimethylamino)cyclohexyl]\u2010<jats:italic>N<\/jats:italic>\u2010methylnaphthalene\u20102\u2010carboxamide) was identified in Australia and the United States. \u03b2\u2010U10 is a positional isomer of \u03b1\u2010U10 (1\u2010naphthyl U\u201047700), more commonly known as \u201cU10.\u201d Here, the first comparative in vitro pharmacological characterization of naphthyl U\u201047700 (U10 and \u03b2\u2010U10), together with the structural analogue U\u201047700 and fentanyl, is reported. Application of a cell\u2010based \u03bc\u2010opioid receptor (MOR) activation (\u03b2\u2010arrestin 2 recruitment) assay demonstrated \u03b2\u2010U10 (EC<jats:sub>50<\/jats:sub>\u2009=\u2009348\u2009nM; <jats:italic>E<\/jats:italic><jats:sub>max<\/jats:sub>\u2009=\u2009150% vs. hydromorphone) to be less potent than U\u201047700 (EC<jats:sub>50<\/jats:sub>\u2009=\u2009116\u2009nM; <jats:italic>E<\/jats:italic><jats:sub>max<\/jats:sub>\u2009=\u2009154%) and fentanyl (EC<jats:sub>50<\/jats:sub>\u2009=\u20099.35\u2009nM; <jats:italic>E<\/jats:italic><jats:sub>max<\/jats:sub>\u2009=\u2009146%) but considerably more active than the \u03b1\u2010isomer (EC<jats:sub>50<\/jats:sub> value in the \u03bcM range). For the latter, maximum receptor activation could not be reached at 100\u2009\u03bcM. The difference in MOR activation potential for U10 and \u03b2\u2010U10 stresses the importance of (analytical) differentiation between closely related analytes. The emergence of \u03b2\u2010U10 on the recreational drug market is an example of the continuing emergence of non\u2010fentanyl\u2010related NSOs and further emphasizes the need to closely monitor fluctuations in the drug supply.<\/jats:p>","DOI":"10.1002\/dta.3554","type":"journal-article","created":{"date-parts":[[2023,7,22]],"date-time":"2023-07-22T01:15:45Z","timestamp":1689988545000},"page":"323-326","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["In vitro \u03bc\u2010opioid receptor activation potential of U10 and \u03b2\u2010U10, positional isomers of the synthetic opioid naphthyl U\u201047700"],"prefix":"10.1002","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1431-441X","authenticated-orcid":false,"given":"Marthe M.","family":"Vandeputte","sequence":"first","affiliation":[{"name":"Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences Ghent University  Ghent Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7126-348X","authenticated-orcid":false,"given":"Christophe P.","family":"Stove","sequence":"additional","affiliation":[{"name":"Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences Ghent University  Ghent Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2023,7,21]]},"reference":[{"key":"e_1_2_7_2_1","volume-title":"European Drug Report 2022: Trends and Developments","author":"European Monitoring Centre for Drugs and Drug Addiction (EMCDDA)","year":"2022"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1097\/ADM.0000000000000324"},{"key":"e_1_2_7_4_1","doi-asserted-by":"publisher","DOI":"10.1097\/PAF.0000000000000787"},{"key":"e_1_2_7_5_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.neuropharm.2017.10.016"},{"key":"e_1_2_7_6_1","volume-title":"The Growing Complexity of the Opioid Crisis. 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