This can cause serious problems even on its own. I don't know if you are familiar with the serious side effects of this class of substances. There are many good informations in the net. I recently saw one of the leading US-experts in german TV on this topic. His name was Charles Bennett. Maybe this helps you for further research. However, I'm not sure if Levaquin can cause CFS. Mostly I hear of neuropathies and joint problems.Treated with Levaquin.