That's interesting. I tolerated it with no problem, but it did take a couple of weeks to get used to. The best part was the pain I was suffering from at the time was totally under control. My biggest problem was that each patch would only last for two days (they're supposed to last for three). As I came down off of the medication, I would get the shakes, feel sick and get really, really tired. I could literally fall asleep standing up. So my doctor increased the frequency to every two days, and then I was fine. The only problem was that some pharmacists were really annoying, since it's a controlled substance, and they would complain that the frequency was too great and give me grief. I did experience some loss of short term memory, which drove people around me a bit crazy. I also had the most amazing dreams and could drift off into daydreams at times almost involuntarily. It was kind of amazing, actually.
I wish I could say that I wrote the next "Xanadu" while on it. But no such luck.
I've read of "functional" heroin addicts who manage to hold down high powered, stressful jobs while hooked on junk. Before taking Fentanyl, I couldn't understand how they did it. Afterwards, I totally got it. I wouldn't abuse it, having had the experience. But I sympathize with what they go through.
BTW, Fentanyl was the drug the Russians used to end that hostage crisis when Chechen terrorists took over a theater in Moscow. They pumped in Fentanyl in gas form into the theater's air ducts. It knocked everyone unconscious (or, at least, made them so high they were incapacitated) and then sent in security forces wearing gas masks. Unfortunately, they didn't have enough emergency medical teams in place, and there were quite a few civilian casualties. I imagine that, if you breathe this stuff in in a concentrated form, it can be pretty lethal.