Abstract
The recent scheduling actions of fentanyl-related substances in both the United States and China have sparked the emergence and proliferation of other generations of “legal” opioids that are structurally distinct from fentanyl, including the recently emerged class of cinnamylpiperazines. In contrast to fentanyl, which contains a piperidine core and a phenethyl moiety, the primary structural components of cinnamylpiperazines are the piperazine core and a cinnamyl moiety. This manuscript reports on the toxicological profile for antemortem and postmortem cases where a cinnamylpiperazine was detected. Samples were quantitatively confirmed using liquid chromatography tandem mass spectrometry. The cases were received between February 2020 and April 2021. Concentrations of 2-methyl AP-237 from four postmortem cases ranged from 820 to 5800 ng/mL, and concentrations of AP-238 from two postmortem cases were 87 and 120 ng/mL. µ-Opioid receptor (MOR) activation potential for 2-methyl AP-237, AP-237, para-methyl AP-237, and AP-238 were studied using a βarr2 recruitment assay. Efficacies (Emax, relative to hydromorphone) and potencies (EC50) were derived and of the compounds tested AP-238 was the most potent compound in the panel with an EC50 of 248 nM. 2-Methyl AP-237 was found to be the most efficacious drug (Emax = 125%) of the tested cinnamylpiperazines; however, it had substantially less efficacy than fentanyl. The in vitro MOR activation potential of the studied cinnamylpiperazines was lower than that of fentanyl and other novel synthetic opioids (NSOs), in line with the relatively higher concentrations observed in postmortem toxicology samples—an important observational link between in vitro pharmacology and in vivo toxicology.
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Acknowledgements
The authors of this manuscript would like to thank the following partners for their contributions: Donna Iula from Cayman Chemical, for gifting of the cinnamylpiperazine reference standards to the Stove group; Christine Murphy from Carolinas Medical Center; Sarah Buxon de Quintana from the LA County Medical Examiner – Coroner office (CA); Michael Yeh from the Georgia Poison Center; Darinka Mileusnic from the Knox County Regional Forensic Center; Di Wang from the Morris County Medical Examiner's Office (NJ); Kelly Boulos from the District 23 Medical Examiner’s Office (NJ), Amy Turenne from the Lake County Coroner's Office (OH); and Robert Johnson from the Tarrant County Medical Examiner’s Office (TX). Daria Morozova is acknowledged for her help in conducting the in vitro experiments.
Funding
Funding for this study was received from the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice (Award Number 2020-DQ-BX-0007, “Real-Time Sample-Mining and Data-Mining Approaches for the Discovery of Novel Psychoactive Substances (NPS)”). The opinions, findings, conclusions and/or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect those of the Department of Justice. M.M.V. and C.P.S. acknowledge the Research Foundation Flanders (FWO) (grant numbers 1S81520N and G069419N, respectively) for funding.
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Fogarty, M.F., Vandeputte, M.M., Krotulski, A.J. et al. Toxicological and pharmacological characterization of novel cinnamylpiperazine synthetic opioids in humans and in vitro including 2-methyl AP-237 and AP-238. Arch Toxicol 96, 1701–1710 (2022). https://doi.org/10.1007/s00204-022-03257-7
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DOI: https://doi.org/10.1007/s00204-022-03257-7