Modafinil drug molecule. Computer model of a molecule of the stimulant drug modafinil. Atoms are represented as spheres and are colour-coded: carbon (green), hydrogen (white), oxygen (red), nitrogen (blue) and sulphur (yellow). Modafinil, which is marketed as Provigil, is used to treat the daytime drowsiness symptoms of narcolepsy, and also attention-deficit/hyperactivity disorder (ADHD). It is thought to work by inhibiting the reuptake of the neurotransmitters dopamine and noradrenaline.