narcolepsy
"I am 30.  I have narcolepsy, fibromyalgia and severe rheumatoid arthritis that is also in my organs. I take 20mg every 4 hours up to 4 times a day.  It takes 30min to kick in, and wears off in 2 hours.  Without it, I felt like I had to curl up on ground wherever I was at or I wouldn't "make it."  With the medicine, I feel totally exhausted, but it takes the edge off the urgency to lay down.  I have been on it for 2 1/2 years.  Docs wan't me off it (since it's a stimulant) and wants me on Nuvigil.  I took one pill 150mg with Ritalin, seemed to help but it's been one day (tapering off Ritalin).  Ued to fall asleep driving every day working full time.  Now  work part time and take methylphenidate and don't fall asleep driving (that I know of)."