Modafinil is approved by FDA for treatment of all except :
Modafinil (Provigil) :

Modafinil is an oral drug that is used for improving wakefulness in patients with excessive sleepiness.
Modafinil is used to promote wakefulness in patients with excessive sleepiness associated with :


Narcolepsy.
Obstructive sleep apnea/hypopnea syndrome and
Shift work sleep disorder.


The exact mechanism of action of modafinil is not clear. It seems that modafinil increases the release of monoamines specifically the catecholamines (norepinephrine and dopamine) from the presynaptic terminals. However, modafinil also elevates hypothalamic histamine levels (in contrast to amphetamine-like stimulant which only releases catecholamines, but not histamine).
Obstructive sleep apnea syndrome (OSAS)
Shift work syndrome (SWS)
Narcolepsy
Lethargy in depression