The FDA approved Xyrem (sodium oxybate) in July 2002 as the first and only treatment for cataplexy in patients with narcolepsy. In November 2005, the FDA approved Xyrem to treat excessive daytime sleepiness in patients with narcolepsy.
The effectiveness of Xyrem for the treatment of narcolepsy symptoms was established in four multi-center, placebo-controlled, studies over a period of time between four and eight weeks. The studies examined three dosages of Xyrem (4.5g per night, 6g per night and 9g per night) taken in two equally divided doses (the first at bedtime and the second 2.5 to four hours later).
Two well-controlled clinical trials demonstrated that Xyrem at doses of 6g and 9g per night is effective at subjectively (as measured by the Epworth sleepiness scale) and objectively (as measured by the maintenance of wakefulness test) improving excessive daytime sleepiness. In addition, two well-controlled clinical trials demonstrated that all dosages of Xyrem significantly reduced the frequency of cataplexy attacks.
Furthermore, patients on the 6g or 9g per night doses saw significant improvements in symptom severity – with the majority of them rating much or very much improved on the clinical global impression of change (CGI-C) in day and nighttime symptoms scale.
Xyrem was also generally well tolerated and no treatment-related serious adverse events were reported.