The approval is significant because most existing narcolepsy medications focus on reducing daytime sleepiness or improving nighttime sleep separately. Scientists believe that approach could eventually help patients with sleep apnea, chronic daytime sleepiness and other neurological disorders linked to disrupted sleep. How the new drug worksNarcolepsy is one of the few neurological disorders with a well-understood cause. The company is already studying orexin-targeting medicines for obstructive sleep apnea, chronic excessive daytime sleepiness and sleep deprivation in otherwise healthy volunteers. Eli Lilly entered the field earlier this year through its $6.3 billion acquisition of Centessa Pharmaceuticals, gaining access to the experimental orexin drug cleminorexton.