muscle spasm
"I found this to be a wonderful muscle relaxant with very few, if any, negative side effects.  It worked well for me during many bouts of chronic back pain that kept me awake at night.  

It did make me a little bit sleepy and dizzy, but nothing that bothered me very much at all.  At night, this wasn't even a concern, but I could easily take it during the day at work and perform and feel fine.

This isn't exactly a "pain" medication but I did find that it worked almost as well for my particular back pain as the narcotic medicines I was also prescribed."