Use and abuse of opioid products has increased alarmingly over the last 20 years, along with deaths due to overdose. Now commonly referred to as the “opioid crisis”, the number of opioid-involved overdose deaths in the US increased 90% from 2013 to 2017. Christine K. Moore and Henry J. Riordan at Worldwide Clinical Trials look at new FDA guidance on endpoints for demonstrating effectiveness of drugs when treating opioid use disorder.