Sentanyl II: A Multi-State Analysis of Fentanyl/Analogs, Naloxone, and Clinical Features of Non-Fatal Opioid Overdose - Abstract The replacement of heroin by fentanyl and its analogs (a.k.a. fentanyls) in the illicit drug supply has disrupted the medical care of non-fatal opioid overdose patients in the pre-hospital, emergency department (ED) and inpatient settings. Concerns that traditional naloxone dosing may be less effective for fentanyls have compelled pre-hospital personnel and ED clinicians to use higher naloxone dosing regimens that are without evidence-based support. In addition, use of fentanyls with other substances in the community is now common (intentionally or unintentionally, as adulterants or concomitant use), and may affect patient naloxone dosing needs and clinical care courses, such as need for medications for agitation and inpatient admission. An in- depth understanding of how fentanyls and concomitant polysubstance exposures affect naloxone dosing needs and clinical care courses would enable the creation of evidence-based guidelines to optimize clinical care. In this UG3/UH3 project, Sentanyl II, we will conduct a multi-state, multi-site, observational study of 905 non-fatal opioid overdose adult ED patients. Sentanyl II is based on our research from Sentanyl/R21DA046734 during which we developed and pilot tested the components (e.g., study protocol, data collection instruments, surveys, discovery testing) that will be employed in this project, and gained the experience to successfully complete this larger scale study. In the UG3 phase on Sentanyl II, we first will adapt and expand the R21 study protocol to obtain more comprehensive information on the treatment received and clinical care course of adult non-fatal opioid overdose patients. We will also incorporate blood sampling for discovery testing along with surveys of participants about their drug use and overdose history into the Sentanyl II protocol. Next, we will conduct a pilot study of Sentanyl II at two University of Massachusetts (UMass) Medical Center EDs. We will revise the study protocol as needed based on our experience and observations in the UG3 phase. In the UH3 phase, we will continue Sentanyl II in the two UMass EDs and expand the project to seven more EDs at three additional study sites with high incidence of non-fatal and fatal opioid overdoses in their locales: University of Florida/Jacksonville, University of Maryland/Baltimore, and West Virginia University. The products of Sentanyl II will be: (1) estimates of the prevalence of fentanyls and other opioids, alcohol, and other illicit and pharmaceutical substances contributing to non-fatal overdoses; and an understanding of how: (2) naloxone administration to the clinically desired response is affected by fentanyls and other opioids, alcohol, and other illicit and pharmaceutical substances, as well as self-reported opioid overdose and drug use history; (3) clinical course is affected by fentanyls and other opioids, alcohol, and other illicit and pharmaceutical substances, as well as self-reported opioid overdose and drug use history. Knowledge obtained from Sentanyl II can assist in the re-evaluation of current clinical practice and aid in the creation of evidence- based guidelines for emergency care.