Modafinil is a prescription medication primarily used to treat sleep disorders such as narcolepsy, obstructive sleep apnea (OSA), and shift work sleep disorder (SWSD). It is a wakefulness-promoting agent that works by altering neurotransmitters in the brain to improve alertness and reduce excessive sleepiness. Modafinil is commonly prescribed for conditions that cause excessive daytime sleepiness, such as narcolepsy, a disorder that leads to sudden and uncontrollable episodes of sleep. It is also used for people with shift work sleep disorder.