Introduction

The USA is in the midst of an opioid overdose epidemic, involving both pharmaceutical opioids and heroin. In addition to efforts to prevent overdoses from occurring, there is an urgent need to prevent overdoses that do occur from turning fatal. Opioid overdose is particularly amenable to intervention because death typically occurs more than an hour after the onset of an overdose, allowing time for resuscitation. Many overdoses are witnessed by others, making timely lifesaving possible. In many cases, however, help comes too late. Sometimes, response is delayed because witnesses do not recognize opioid overdose symptoms as life-threatening, or because they fear legal consequences of calling 911.