Narcolepsy is associated with disrupted nighttime sleep (DNS). Sodium oxybate (SXB; Xyrem®), administered twice nightly, is indicated for the treatment of cataplexy and excessive daytime sleepiness in patients 7 years or older with narcolepsy. Recently, low-sodium oxybate (LXB, Xywav®; for people 7 years of age and older), which contains 92% less sodium than SXB and is dosed twice nightly, and sodium oxybate for extended release (SXB-ER; Lumryz™; for adults), which contains equal sodium to SXB and is dosed once nightly, have also been approved to treat cataplexy or excessive daytime sleepiness in narcolepsy. This paper reviews the evidence regarding the overall impact of oxybate administration, and impact of different oxybate dosing regimens (once nightly, SXB-ER; twice nightly, SXB), on DNS in narcolepsy utilizing polysomnographic data from five clinical trials (three assessing SXB in adults [referred to here as SXB trials 1, 2, and 3], one assessing SXB in children [referred to as the pediatric SXB trial], and one assessing SXB-ER in adults [REST-ON]). Both once-nightly and twice-nightly oxybate regimens similarly improved symptoms of DNS. Regardless of dosing regimen, people with narcolepsy treated with oxybate experience roughly 42-53 arousals and 9-38 awakenings each night, with one of these awakenings on twice-nightly oxybate being due to the second dosing requirement in studies of SXB. Additionally, for SXB, but not SXB-ER, polysomnographic data has been analyzed by half of the night, demonstrating a greater positive impact on sleep architecture in the second half of the night, which might be related to its nonlinear pharmacokinetic profile. We conclude that while once-nightly and twice-nightly oxybate dosing regimens differ in their pharmacokinetic profiles, both improve DNS in patients with narcolepsy to a similar degree.
Keywords: Disrupted nighttime sleep; Low-sodium oxybate; Narcolepsy; Nocturnal; Polysomnography; Sodium oxybate.
Narcolepsy causes daytime sleepiness and difficulty sleeping (commonly called disrupted nighttime sleep). Sodium oxybate (Xyrem®) and low-sodium oxybate (Xywav®, which contains 92% less sodium than sodium oxybate), are taken twice nightly in patients with narcolepsy. Sodium oxybate for extended release (Lumryz™), which contains as much sodium as sodium oxybate, is taken once per night. All three medications improve narcolepsy symptoms and have the same active ingredient. It is important to understand how well they improve nighttime sleep.This review examined results of five clinical studies looking at disrupted nighttime sleep in people with narcolepsy: three of twice-nightly sodium oxybate in adults (called SXB trials 1, 2, and 3 here), one of twice-nightly sodium oxybate in children (called the pediatric SXB trial here), and one of once-nightly sodium oxybate for extended release in adults (called REST-ON here). No studies specifically investigated disrupted nighttime sleep with twice-nightly low-sodium oxybate in people with narcolepsy. Although the trial designs for these studies were different, both twice-nightly and once-nightly oxybate medications improved sleep similarly, and neither eliminated arousals or awakenings. Certain aspects of sleep improved more during the second half of the night in SXB trials 1 and 3 compared with the first half of the night. Both once-nightly and twice-nightly oxybate medications similarly improve nighttime sleep in people with narcolepsy. Twice-nightly oxybate may be particularly helpful in improving sleep in the second half of the night.
© 2023. The Author(s).