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How effective is Xywav for Idiopathic Hypersomnia?

Medically reviewed by Carmen Pope, BPharm. Last updated on Nov 23, 2022.

Official answer


Xywav stops people with idiopathic hypersomnia from feeling sleepy during the day with an average improvement in the Epworth Sleepiness scale (ESS) of 7 points. The ESS is a subjective measure of your risk of falling asleep during activities such as watching TV, talking to someone, or while in a car, and scores from 0 (no chance at all of dozing) to 24 (excessive sleepiness that requires medical attention). A score of 10 or higher suggests idiopathic hypersomnia.

Trails looking at the effectiveness of Xywav administered it to everybody to start with, then stopped it in approximately half. The median improvement in ESS score was 6.5 in those who took Xywav compared to 5 in those taking a placebo (an inactive treatment) during the stable dose period. At the end of the double-blind withdrawal period, the difference in ESS between those who stopped Xywav and those who kept taking it was 7 points, indicating a worsening of daytime sleepiness in those who stopped it. Of those that took Xywav, 79% said overall their symptoms of idiopathic hypersomnia, such as long sleep time, cognitive impairment, and sleep inertia improved.

Idiopathic hypersomnia is a condition that causes you to be very sleepy during the day even after a good night’s sleep. It can also cause difficulty waking up after you've been asleep.


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