Below is a expert from a book the Mayo clinic put out for Arthritis. They give a reason of why AntiBiotics help relieve pain and stall/stop progression. I consider FM a type of arthritis. Interesting excerpt below and full article below that. ****************** research has shown that some antibiotics may be helpful in some forms of arthritis because they suppress enzymes and other proteins know to cause inflammation. ****************** Antibiotics Scientists continue to explore the possibility that some for of infection might trigger the onset of rheumatoid arthritis. If so, perhaps takeing a certain antibiotic might prevent the disease. Building on this theory, some researchers are testing whether antibiotics can suppress progression of the disease and relieve symptoms. Most of the common forms of arthritis are not caused by the presence of bacteria in the joint, causing inflammation. Still, research has shown that some antibiotics may be helpful in some forms of arthritis because they suppress enzymes and other proteins know to cause inflammation. Minocyclin is an antibiotic that also may help people who have early rehumatiod arthrits. Commonly used to treat acne, minocycline seems to provide a meaure of relief from joint swelling, stiffness and pain. Likes its cousin doxycycline, minocycline is an antibiotic that seems to block enzymes (called metalloproteinases) that destroy cartilage inside your jounts. Researchers believe that this drug may slow or prevent joint damage that occurs in th both osteoarthritis and rheumatoid arthiritis. Future research will be needed to determine whether these medications work because of their antibiotic activity or because of some other process. We also need identify who can benefit most from them and how to use them safely with other arthritis medications.