EpidemiologyEpidemiology

The epidemiology of opioid misuse and OUD has several important implications for product liability. First, opioids have had, and continue to have, established clinical utility. This is quite different from most other products subject to product liability claims and litigation, where defective or excessively high-risk products are removed from the market. Second, the prevalence of NPOU (4–10%), opioid misuse (3–4%), and OUD (2–3%), while concerning from a public health perspective, is largely aligned with adverse event rates for many prescription drugs. While these rates have remained relatively stable in recent years, the rates of prescription opioid utilization have fallen precipitously, suggesting that OUD rates have been buoyed by the incursion of illicit opioids, including heroin and fentanyl. Rapidly declining rates of prescription opioid utilization over the past decade are due mainly to changes in clinical practice guidelines, increased oversight on the part of state and federal regulators (who had largely failed in their oversight role in the years leading up to the crisis), and other programs, such as public awareness campaigns and drug take-back programs. The economics of externalities provides a useful conceptual lens through which to view the harms identified by epidemiologists. From the externality perspective, claimants are essentially arguing that defendants increased the supply of opioids, which in turn increased the prevalence of OUD. However, OUD is a negative externality associated with three distinct source pathways, sources that in many cases cannot be reliably differentiated ex post. Perhaps more importantly, OUD is comprised of three sub-components, only one of which is associated with measurable harms. Opioids have clinical utility and continue to be utilized in clinical settings in response to legitimate medical needs. In some cases, some individuals develop OUD, but most opioid users do not. Individuals at greater risk for OUD include those with pre-existing conditions related to substance use disorders and mental health conditions. The causal pathway from opioid supply to public nuisance-causing OUD is considerably more complex than the standard epidemiological causal model. First, for an opioid to get into the hands of a consumer, it travels through a labyrinth of regulatory oversight by federal and state governing bodies and accreditation agencies, followed by organizational control by payers, health systems, and physicians, who establish clinical norms and standards regarding medical appropriateness of treatment. As such, medical products are among the most heavily controlled and monitored products in the U.S. To say that one segment of the supply chain failed is to say that all or most pieces of the system failed, as each segment is intertwined in multiple ways with the others. Second, as discussed in Chapter 2 and again at the end of this chapter, there are at least 20 different causal variables that contributed to the increase in opioid supply from approximately 1995 to 2012.