Modafinil is a wakefulness-promoting agent (or eugeroic) used for treatment of disorders such as narcolepsy, shift work sleep disorder, and excessive daytime sleepiness associated with obstructive sleep apnea. It has also seen widespread off-label use as a purported cognition-enhancing agent.

Because of the risk for development of skin or hypersensitivity reactions and serious adverse psychiatric reactions, the European Medicines Agency has recommended that new patient prescriptions should only be to treat sleepiness associated with narcolepsy.

Allergy and hypersensitivity are the only contraindications of the drug, but literature distributed by Cephalon advises that it is important to consult a physician before using it, as problems may arise for people who are sensitive to constituents of the tablets, people with cirrhosis (which may impair the metabolism of the drug), and people with various cardiovascular problems.