I've been taking methadone for severe shoulder pain from 2 surgeries for a few years now. It's worked pretty good, and I don't have to worry about the "high" feeling I got with the narcotic ones. However, I went to the dentist one time for a procedure, and I wanted to use "gas." It wouldn't work, even on the highest setting. I've also not had narcotic shots in the hospital not work. I may have to have another surgery on my shoulder, and I'm scared that the methadone will not allow the gen anastetic work. What are the odds of this happening?