OpTrak: Tracking Opioid Prescriptions via Distributed Ledger Technology Peng Zhang, Breck Stodghill, Cory Pitt, Cavan Briody, Douglas C. Schmidt, and Jules White Vanderbilt University, USA Alan Pitt, MD Barrow Neurological Institute, USA Kelly Aldrich Center for Medical Interoperability, USA ABSTRACT This paper describes the structure and functionality of OpTrak, which is a decentralized app (DApp) implemented using the Ethereum blockchain that targets the opioid epidemic currently plaguing the United States (US). The US has a severe problem stemming from the over prescription and distribution of opioids, costing the national healthcare system over $78 billion every year. Problems persist in every stage of the process, from doctors prescribing the medication to pharmacies fulfilling prescriptions. These problems arise from a combination of factors, including lack of accountability, transparency, and reliability in the current prescription drug monitoring programs. This work provides three key contributions to research on a technical approach to mitigate the opioid epidemic in the US. First, we pinpoint key problems and loopholes that exist in the current opioid prescription system. Second, we propose an integrated approach for addressing these problems by leveraging the disintermediation, immutability, and network consensus characteristics of distributed ledgers, focusing on blockchain technology. Third, we describe the structure and functionality of a DApp, called OpTrak, that allows a consortium of healthcare providers to exchange patient prescription data securely. Our initial DApp prototype logs prescription data access requests and responses on a private configuration of the Ethereum blockchain and provisions access to patient data accordingly across a network of providers. Keywords: Opioids, Opioid Epidemic, Blockchain, Ethereum, Smart Contract, Healthcare, Data Sharing, Interoperability, Prescription Drug Monitoring Programs INTRODUCTION Emerging trends and challenges. It is widely known that the United States (US) is in the midst of an opioid epidemic. Opioids are a class of drugs that consists of heroin, as well as legal pain relievers like oxycodone, hydrocodone, codeine, and morphine. Pain relieving opioids can be safe when prescribed for the right reasons and duration. These opioids can easily be misused, however, due to the production of euphoria and the relief of pain. Due to these effects, regular use (even through valid prescriptions) can yield dependence and addiction. In turn, the abuse of pain relievers often leads to overdose and death (National, 2018). Every day in the United States, over 115 Americans die after overdosing on opioids (CDC/NCHS, 2017). Moreover, the DEA states that up to 80% of heroin addictions begin with the misuse of prescription opioids (Bresnick, 2017). By calculating the costs of healthcare, addiction treatment, lost productivity, and criminal justice involvement, The US Centers for Disease Control and Prevention