Modafinil. Molecular model of the drug modafinil (C15.H15.N.O2.S). This wakefulness-promoting agent is sold under the brand name Provigil. It is used for treatment of disorders such as narcolepsy, shift work sleep disorder, and excessive daytime sleepiness associated with obstructive sleep apnoea. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red) and sulfur (yellow).