Buy Provigil It is commonly used for the following conditions. Obstructive sleep apnea is a disorder that happens when your breathing stops and starts while you sleep because your airway gets blocked. Narcolepsy, a condition in which your brain’s control of your sleep-wake cycle is not working. Shift work disorder, a condition (mostly in people working night, early morning, or rotating shifts), involves trouble sleeping when you need to and/or extreme sleepiness when you need to be awake.