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