Guaifenesin
"I have been using Guaifenesen for 10 years now. Like my  Doctor said, I had initial relief, then cycled between feeling worse and better, and now my CFS / Fibro is much milder than it was.  I avoid Salicylates, but accidental exposure  isn't a disaster, since I am not a strong blocker.  For me, it works best just before or just after mild exercise, like a 1 mile walk to work, or mowing the lawn. I take 1/4 of a COSTCO 400 mg. Tablet whenever I feel Fibro pain, or before anticipated exercise, or after unexpected exercise."