Funny, I happened to need fentanyl a few weeks ago for the aftermath of a medical procedure. The nurse in recovery room added it to the IV drip, then added more (I had a lot of pain), and then I remember the nurse waking me up and telling me to breathe. Even at the very carefully measured hospital doses, my body was forgetting that it needed to breathe. That is powerful stuff.
The other thing about fetanyl is that it wears off in like 40 minutes. Which is great for hospitals and acute pain. But it makes it really diabolical as a street drug, because people inject it, and, if they survive, they want to inject some more in half an hour. It's like the perfect drug for killing people.
At this point the government shouldn't just legalize marijuana, they should provide for free to anybody willing to try it as a substitute for whatever other street drugs they're taking. They could save a lot of lives. Of course the fools in Washington are going to just the opposite, crack down on marijuana and throw another million people in prison.