chronic fatigue syndrome
"Got a trial prescription for Nuvigil 150mg tablets, first day was incredible, but after a few days the effectiveness was greatly diminished.  Still worked but did not have the same effect as day one.  Worried about using it regularly since it is not covered by insurance and without that the cost is outrageous ($330/30 tablets).  Does not leave you nervous like Ritalin, and lasts longer than Provigil. Worth trying if your health care plan covers it."