Alot of people say that the caffeine takes away from the opiate feeling. I personally don't know because I was prescribed the Tylenol 3's. I'm more of a Tramadol guy but when I took a few of the T3's, I felt nice and warm for a couple hours. They didn't last that long at all, but then again, like I said, my doc has been Tramadol for a few years now.