narcolepsy
"Provigil (Modafinil) has been a good addition to my regimen for dealing with the symptoms of narcolepsy.  I take different doses depending on severity of symptoms.  I take 50 mg. twice a day most of the time.  Or 100 mg. twice a day.  I have tried 200 mg. once or twice a day and that's where the side effects kick in (very dry mouth and headaches).  It does keep me awake during the day most of the time, but sometimes I feel as if I never took it.  But that's where adding coffee or caffeine pills really helps.  I feel safe taking this med and I'm happy to have discovered it."