SLC6A3 and narcolepsy: Modafinil (MO; 2-[(diphenylmethyl) sulfinyl] acetamide), an inhibitor of the dopamine transporter, is a wake-promoting drug, which was approved by the Food and Drug Administration (FDA) in 1998 for treating excessive daytime sleepiness in narcolepsy and other sleep disorders, such as shift work sleep disorder and obstructive sleep apnea syndrome (Minzenberg and Carter, 2008).