Modafinil, sold under the brand name Provigil among others, is a wakefulness-promoting drug used for treatment of disorders such as narcolepsy, shift work sleep disorder, idiopathic hypersomnia, and excessive daytime sleepiness associated with obstructive sleep apnea. It has also seen widespread off-label use as a purported cognitive enhancer. In the United States modafinil is classified as a schedule IV controlled substance and restricted in availability and usage, due to concerns about possible addiction potential. In most other countries it is a prescription drug but not otherwise legally restricted.
Modafinil acts as an atypical, selective, and weak dopamine reuptake inhibitor which indirectly activates the release of orexin neuropeptides and histamine from the lateral hypothalamus and tuberomammillary nucleus, respectively, by unknown mechanisms, all of which contribute to heightened arousal.