Modafinil is a stimulant medication that promotes wakefulness and is most commonly used to treat the symptoms of sleep/wakefulness disorders. Modafinil, for example, has been approved by the FDA to treat chronic fatigue, excessive daytime sleepiness (narcolepsy), obstructive sleep apnea, and shift-work sleep disorder. Modafinil is an FDA-regulated substance in the United States, and it can only be legally obtained and used with a doctor's prescription. When it comes to the legitimate medical use of modafinil, it is generally believed to have minimal side effects and a lower potential for abuse and addiction when compared to other psychostimulant medications — that's one of the reasons that modafinil has been officially FDA-approved for the treatment of certain medical conditions.