physiological chemical changes during an opiate overdose that could be used to trigger life saving antagonist already on board.

[neversickanymore]

What chemical changes caused by opiate overdose, could be used to trigger a chemically enveloped antagonist already on board?

 

[neversickanymore]

I guess another option would be tech based device that would automatically administer the the antagonist based off biometrics that are readily available from smart devices. Sounds good In theory, but im not sure real life would work that well as how do you get users to wear them.