is one of the stimulants used medically in the treatment of narcolepsy
. It holds the promise of allowing people who suffer from unusual fatigue to remain awake without side effects or impairment of job performance
. However it does not live up to this promise in all cases, occasionally producing rashes, intestinal problems and other side effects. The usual prescription is for one pill to be taken shortly after waking; its effects last for most of the day, but do not usually prevent the person from going to sleep at a normal time. It is prescribed under the trade name Provigil ®.