The psychostimulant modafinil stimulates the orexin neurons. Orexin neurons, which regulate alertness and sleepiness, are found in the brain. By stimulating orexin neurons, modafinil improves wakefulness and lowers your risk of developing sleep attacks.   If advised by your doctor, take one Modalert 200 mg tablet. When taking the medicine, sip some water. Give up chewing or crushing the...