Modafinil is a non-amphetamine central nervous system (CNS) stimulant used to improve wakefulness in patients with sleep apnea, narcolepsy, or shift work disorder. The exact mechanism of action is unclear, although in vitro studies have shown it to inhibit the reuptake of dopamine by binding to the dopamine reuptake pump, and lead to an increase in extracellular dopamine. The high concentration of dopamine activates D2 receptors on the post-synaptic membrane leading to activation of the Gi signaling cascade. This cascade is inhibitory and ultimately leads to the inhibition of sleep, promoting wakefulness. This action of modafinil is its primary clinically important property. Modafinil is generally a well-tolerated stimulant. The most commonly reported adverse effects of modafinil (less than 10% of users) are a headache, nausea, and decreased appetite. Other commonly reported adverse effects (5% to 10% of users) include anxiety, insomnia, dizziness, diarrhea, and rhinitis

Modafinil Pathway References