Guaifenesin
"After suffering unbearably for 15 years  from Fibromyalgia (including 6 years on disability for it). My neurologist suggested I read everything by Dr. D'Amato and try Mucinex.  We tried 600 mg twice a day for 6 weeks, no response, upped the dose to 800 mg twice a day for 4 weeks, a little better, then 1200 mg twice a day and it was a miracle.  I slowly regained a life again.  Throughout this time I also exercised about 1/2 hour a day, which also helps."