Naltrexone was approved by the FDA in 1994 for the treatment of alcohol dependence. Despite the potential to make treatment more effective and accessible, naltrexone use remains low by almost any measure. While many of the factors responsible for the slow pace of diffusion are unique to naltrexone and to the organization and delivery of alcohol treatment services, other factors are the same as those that affect the use of prescription medications more generally. Access to third-party coverage and formulary inclusion are necessary conditions for the adoption and diffusion of any new pharmaceutical technology. This paper describes current issues in drug benefit design and formulary coverage decisions, reviews publicly available information on naltrexone coverage by large health insurance programs and pharmaceutical benefit management companies, and examines whether drug benefit design constitutes a barrier to naltrexone use. Our review suggests that naltrexone is widely covered on public and private health plan formularies, though restrictions on use (i.e., quantity limits, prior authorization) are common.