Modafinil is a psychostimulant used in the treatment of narcolepsy and idiopathic hypersomnia. It was tested on a thousand French soldiers during the Gulf War in 1991, even without the drug was authorized. It allows people who suffer from unusual fatigue to stay awake with little or no side effects. The usual prescription is a pill from awakening; its effects last most of the day, but does not prevent the person from sleeping at normal hours. His mechanism of action is still little known. It is similar to sympathomimetic agents, such as amphetamines or methylphenidate, although its pharmacological profile is not identical. Its central stimulating effect depends on the dose and time. The effect tends to be increased by chlorination but reduced by methylation. Modafinil blocks the reuptake of norepinephrine, dopamine by noradrenergic and dopaminergic terminals into neurons that cause sleep in the preoptic ventrolateral nucleus.