A wearable system detects an opioid overdose and transmits a distress message with the wearer's GPS coordinates to one or more emergency response contacts. Concurrently, the system signals a switch which energizes a solenoid injector, causing a prescribed dosage of an opioid antidote to be injected by a syringe into the wearer's body. Detection of an opioid overdose is based on one or more symptomatic biometrics, which are measured by a wearable monitor. The monitor unit and the injector units can be separate, or they can be combined in a single unit.