system
Given the following post, respond as if you're commenting on Reddit:
human
What happens when we overdose?

In light of recent events.  What happens when people overdose.  Do we have the most amazing high then everything goes black?  Or is there a lot of suffering before you go unconscious?
gpt
Heroin overdose is similar to any opiate overdose. Opiates depress the central nervous system causing a relaxed, "euphoric" sensation. After the initial rush, breathing becomes more shallow, decreasing oxygen to the brain and rest of the body. Without oxygen, the brain will start shutting down systems, including the nervous system. The individual will feel extremely drowsy and slip into a coma state. At this point, the nervous system is so relaxed that it fails to function. The individual goes into respiratory arrest (completely stop breathing). Once this occurs, no oxygen is being brought into the body and systems shut down and death occurs shortly after.

TLDR: Opiates relax the nervous system. Heroin overdose would be the same sensation as being so drowsy that you fall asleep.