I just saw an excellent episode of the Nature of Things with David Suzuki on Sunday night. It was about medicinal marijuana and was extremely informative. I gleaned one or two guidelines for those of us who do this, but aren't on any kind of authorized user list.
The main one was to start out slowly. Take two puffs. Wait a while to see if it works and take two more if needed. Keep going that way until you find out how much you need to get the muscle relaxant effect going.
Just thought I'd pass that along.