Cassidy TA, et al. – The reformulation of oxycodone hydrochloride controlled–release (CR) tablets in August 2010 created a natural experiment at a national scale, providing an opportunity to evaluate patterns of abuse of prescription opioids and other drugs before and after introduction of this abuse–deterrent formulation (ADF). Replacement of a widely prescribed opioid formulation known for its abuse potential alone may have had little impact on overall rates of prescription opioids as a class. However, changes in abuse levels of certain opioids coinciding with ADF introduction suggest possible switching of abuse among this study sample to specific long–acting opioid analgesics. Additional follow–up studies will be important to monitor changing abuse patterns and their public health impact as new opioid formulations are developed and introduced to market.