Sodium Oxybate Relieves Pain Symptoms of Fibromyalgia

SAN DIEGO?Sodium oxybate (Xyrem)? currently indicated for the treatment of excessive daytime sleepiness and cataplexy symptoms in patients with narcolepsy?appears to relieve the pain associated with fibromyalgia, based on results of a short-term study presented at the 22nd Annual Meeting of the American Academy of Pain Medicine.

In this 8-week, randomized, placebo-controlled, double-blind trial involving 188 patients with fibromyalgia, use of sodium oxybate, 4.5 or 6 g/day, resulted in significant improvements in health outcome measures, including pain scores, sleep quality, and overall well-being, compared with placebo.

"Fibromyalgia is notoriously difficult to treat. The fact that this study demonstrated significant benefits in symptoms involving pain and some of the broader quality-of-life issues was encouraging," lead investigator Patrick Wood, MD, of Louisiana State Uni?versity Health Sciences Center, Shreveport, told IMWR.

The primary outcome measure was a composite of end points that included visual analog scale (VAS) score for pain (captured with electronic diaries), Patient Global Impression of Change, and the Fibromyalgia Impact Questionnaire total score. Secondary measures included Ten?der Point Count (TPC), Tender Point Index (TPI), and measures of sleep efficiency and overall well-being.

All patients underwent overnight sleep analysis by poly?som?nography to rule out obstructive sleep apnea or parasomnias; symptoms of these conditions would exclude the use of this drug.

Patients were randomized to 3 groups: 58 patients (~95% women; mean age, 46 years) received sodium oxybate 4.5 g/day; 66 patients received the 6-g/day dose; and 64 received placebo.

Those taking either of the active doses had an approximate 25% reduction in VAS pain score compared with a 12% reduction in the placebo group. In addition, TPC and TPI tender point scores demonstrated a strong trend toward improvement, with about a 25% reduction in both scores; those receiving placebo had an 11% decrease in TPC score and a 17% decrease in TPI score.

The group taking 6 g/day of sodium oxybate reported more nausea, vomiting, headache, and dizziness compared with the 4.5-g/day and the placebo groups, but most adverse events were mild or moderate and transient.

Key points

Fibromyalgia is a challenging condition for patients and ?physicians alike.

This is the third study to show that sodium oxybate relieves pain in fibromyalgia.

Keep in mind that this is an ??off-label use.

Nausea was the most common side effect in this study.

"I am a primary care physician, and patients with fibromyalgia comprise a significant part of my practice, which I believe is highly representative of what is happening nationally in the primary care community. Both physicians and pa?tients are desperate for something that will offer hope, and this drug has shown to be promising," Dr Wood noted.

"Increased fatigue and excessive sleepi?ness occurred in some patients, but nausea was the number one side effect," he added. "This is an off-label use. Physicians need to do their homework. I use it off-label, and I think it is safe. This is the third study looking at this agent for fibromyalgia, and they have all been positive."

Sodium oxybate was initially approved in 2002 for cataplexy in patients with narcolepsy. It received an expanded indication in November 2005 for the treatment of excessive daytime sleepiness ?associated with narcolepsy.