Buy Provigil Online. It is a brand name for the generic medication modafinil. It is primarily used to treat excessive sleepiness caused by conditions such as narcolepsy, obstructive sleep apnea, and shift work sleep disorder. Provigil works by affecting certain chemicals in the brain that control wakefulness and sleep. It promotes wakefulness and alertness, helping individuals stay awake and reduce daytime sleepiness. Provigil works by affecting certain chemicals in the brain that regulate sleep and wakefulness. It is believed to promote wakefulness and alertness by increasing the levels of dopamine and norepinephrine in the brain.