Modafinil is a medication primarily used to promote wakefulness in individuals with sleep disorders such as narcolepsy, obstructive sleep apnea, and shift work sleep disorder. It is also sometimes used off-label to enhance cognitive function and alertness in people without sleep disorders. Modafinil is FDA-approved for the treatment of excessive daytime sleepiness associated with narcolepsy. It may be prescribed to improve wakefulness in people with this condition who experience excessive daytime sleepiness despite adequate treatment of their underlying sleep apnea. Modafinil can help individuals who work irregular hours to stay awake and alert during their work shifts.