Final answer:
Modafinil (brand name: Provigil) is approved for treating narcolepsy.
Step-by-step explanation:
A. narcolepsy
Modafinil (brand name: Provigil) has been approved for treating narcolepsy. Narcolepsy is a neurological disorder that affects the sleep-wake cycle, causing excessive daytime sleepiness and uncontrollable episodes of falling asleep. Modafinil is a psychomotor stimulant drug that helps promote wakefulness and decrease the symptoms of narcolepsy.