Sodium oxybate improves symptoms of fibromyalgia

Clinical question Does sodium oxybate improve symptoms in patients with fibromyalgia?

Bottom line In highly selected patients with fibromyalgia, sodium oxybate (Xyrem) improves symptom scores. Sodium oxybate is a schedule III drug and is only available through the manufacturer with tight eligibility and monitoring requirements. (Level of evidence = 2b)

Synopsis Adult patients meeting the American College of Rheumatology criteria for fibromyalgia and with pain scores higher than 40 on a 100-point visual analog scale were randomly assigned to receive an oral solution of sodium oxybate (4.5 g or 6 g) or placebo (matched to active treatment by volume). Because sodium oxybate has a short half-life (30-60 minutes), patients were asked to set an alarm to take a second dose 2.5 to 4 hours later. Patients with comorbid conditions were excluded. During the 8-week study period, patients were asked to not use opiates, tramadol, antidepressants, or muscle relaxers, but were permitted to continue massage, acupuncture, physical therapy, or other behavioral and cognitive therapies. Additionally, they were allowed to use one OTC analgesic for rescue purposes. The study inclusion and exclusion criteria and participation requirements likely resulted in patients who are not like the patients with fibromyalgia we see in the real world. The main outcome measure, assessed via intention to treat, was a 20% reduction in a composite score for changes from baseline in 3 coprimary self-report measures: patient's pain rating (in daily electronic diaries) on a visual analog scale, the Fibromyalgia Impact Questionnaire score, and the Patient Global Impression of Change. This threshold is consistent with the minimal clinically important difference. In patients taking 4.5 g sodium oxybate, 34.5% had 20% improvement compared with 27.3% of those taking 6 g sodium oxybate, and 12.5% of those taking placebo. The numbers needed to treat are 5 (95% CI, 3-122) and 7 (4-107), respectively, for the two treatment groups. It is unclear why the lower dose was more effective. There were comparable improvements in many other measures of symptoms and function. However, there were no reductions in the number of tender points. Patients taking the higher dose were more likely to experience adverse events. Nausea and dizziness were the most common side effects. Only one patient had a serious adverse event.

Russell IJ, Perkins AT, Michalek JE; Oxybate SXB-26 Fibromyalgia Syndrome Study Group. Sodium oxybate relieves pain and improves function in fibromyalgia syndrome: a randomized, double-blind, placebo-controlled, multicenter clinical trial. Arthritis Rheum. 2009;60(1):299-309.