"Fibromyalgia is notoriously refractory to treatment," said lead investigator Patrick B. Wood, MD, assistant professor of family medicine at the Louisiana State University Health Sciences Center in Shreveport, Louisiana.

The researchers hypothesized that sodium oxybate would regulate neurotransmitter levels required for normal sleep cycles, which are frequently disrupted during stage III and IV sleep in people with fibromyalgia.

"This study demonstrates a pretty novel application of this drug," said Dr. Wood, but he acknowledged that some clinicians have used the drug off label for fibromyalgia.

In the double-blind, multicenter study, 150 fibromyalgia patients were randomized to receive 4.5 g or 6 g of sodium oxybate or placebo. They filled out a daily electronic diary reporting pain and fatigue visual analog scale scores as well as rescue medication use. Other measures of sleepiness, function, and global impression were recorded at office visits throughout the 27-day study.

Both doses of the drug resulted in significant reductions in pain, fibromyalgia impact scores, and patient-reported change in global impression scores compared to placebo.

There was a strong trend toward significant reductions in tender point count and tender point index. The sodium oxybate group reported 1.5 fewer tender points on average and about a 3-point reduction in tender point index score compared with the placebo group. Sleep scores were about 2 points lower on average for the active treatment arm.

There was a dose-dependent increase in nausea, vomiting, headache, and dizziness for patients receiving sodium oxybate compared with those who received placebo.

The authors cautioned that this is preliminary, proof-of-concept data. They are currently designing further studies to determine sodium oxybate's efficacy in treating fibromyalgia.

Orphan Medical, a subsidiary of Jazz Pharmaceuticals, sponsored this study.


[Presentation title: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Multi-Center Trial Comparing the Effects of Orally Administered Xyrem (Sodium Oxybate) With Placebo for the Treatment of Fibromyalgia. Poster 121]

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