I have been on opioids since my nasty car crash in 2015 and I am now on Hydromorphone and a larger daily dosage of it to try and control 24/7 chronic pain. The Hydromorphone on a rare occasion makes me sleepy. But really controls the pain.
My guess is Fentanyl would just make a person so sleepy that one would just drift off to sleep. The problem after that, like all opioids is the opioids receptors in one's brain basically get "overloaded" and the electric signals that go to one's diaphragm slow down and stop i.e. no breathing.
Now also it depends if one is opioid naive or not. I have been on them since 2015 and I take 12 mg of Hydromorphone to start the day as the pain when I wake up is always REALLY going. 12mg of Hydro in an opioid naive person and the person would have a really good chance of not waking up.
I will NEVER go on Fentanyl, as the withdrawal from it is hellish. That is one reason that I am still on Hydro because moving me to another drug would be awful as I would still have withdrawal because of the dosage that I am on. Same with fentanyl, it is SO strong that withdrawal is HELL.
Very long story short, if you are opioid naive, and you got your hands on 1 patch and disassembled the patch and swallowed the contents, instead of putting it on your skin, there is a high probability of saying goodbye.
The strongest analog of Fentanyl is Lofentanil. Now THAT would cause death period.
Walter