About a week and a half ago I went to the emergency room with blinding abdominal pain accompanied by frequent vomiting and that intense feeling you get of things being not right. Turns out I had kidney stones and an infection to go with them. At the ER, I got a prescription for Vicodin, among other things, to deal with the pain, but I didn't get it filled right after being discharged because I've tried Vicodin before for my fibromyalgia pain and it does nothing whatsoever to alleviate the pain, but it does make me vomit, and I was doing enough of that already.
After I was discharged from the ER, though, the pain got bad again quickly and I eventually sent my husband to the pharmacy to pick up my Vicodin prescription. I took it, and it dramatically reduced the amount of pain I was feeling from the kidney stones. However, at the same time I was in pain from my fibromyalgia because I'd been laying down for over twenty-four hours at that point, with breaks only to go to the bathroom or vomit. My shoulders and back were compressed from being immobile and the pain grew to the point where it was about 3/4s as bad as the kidney stone pain was without any medication at all. Once I took the Vicodin, the kidney stone pain was reduced by 85% or more, but the fibromyalgia pain was not affected at all, just like usual. I only had one episode of vomiting that I think was due to the medications, too; despite the lack of relief of my fibromyalgia pain, I was pretty pleased with this outcome.
I assume doctors are aware of this difference in medication efficacy between pains; thinking on it, they must be, or why would they develop drugs like Lyrica specifically for nerve pain? I haven't heard a doctor articulate this difference before, though, and you'd think that, as a patient with a chronic pain condition, I would have a fair chance of hearing it if they were in the habit of talking about it. It makes me curious, though, if whether in my lifetime I will see the development of pain treatments that acknowledge all the different kinds of pain. I have this theory that the way our bodies sense pain is much more complicated than medical science currently acknowledges. My experience with kidney stones suggests that if you view opiates like Vicodin as acting primarily to block pain receptors in the brain so that pain signals don't get through (which I believe is more or less accurate), there has to be more than one set of pain receptors, or more than one way in which those receptors accept information, and perhaps whole different systems built for sensing different kinds of pain.
In Pain: the Science of Suffering, by Patrick Wall, Dr. Wall describes the traditional medical model for pain as something like a contraption where at one end you knock a ball with a hammer to start it rolling on its path and then at the other end once the ball gets there it rings a bell: injury equals nervous system reaction equals pain. This traditional model is clearly sadly lacking, and often cruelly misleading, and I'm interested to see what medical science is going to discover to put in it's place.