It contains guaifenesin. A Dr. St. Amand, MD feels that this can fix FMS. He wrote a book years ago about this. OHSU Medical Center in Portland, OR has a FMS Treatment Center. They do a lot of research there under Dr. Robert Bennett, MD mostly. He is a rheumatologist. They did a year long study on this medicine, and found it did not work any better than a placebo. Dr. St. Amand was consulted in setting up the study, but after the results came in he said it didn't work because he had since discovered that one must avoid contact with salicylates or the guaifenesin would not work.
My problem with that is that he claimed the guai worked fine before that study was done, when he was not having his patients avoid salicylates.
Anyhow, the article witten about this study can be found at the site http://www.myalgia.com and you can read it for yourself.
If and when Dr. St. Amand, MD does his own study that proves his theory that this stuff works, I will read it and maybe even try this stuff. I have not found people who have been on this protocol for years and have been able to stop all their FMS meds and are doing well, back to work, etc.
There are few and uncommon side effects, so I don't think there is much harm in trying this if you want to.