I had morphine once, when I had a burst appendix, suddenly the pain was gone and I felt really really good, I think I started singing or something.
I remember taking a strong ampethemine once, it felt like life, good powerfull life, was suddenly coursing through my veins, that made me feel good.
It may not be the best analogy, and its probably a bit blaspemous as well, but its the best I could come up with, that discribes an externaly administered reaction to prayer, that brings such a profound feeling in your body and mental high.