Sodium oxybate relieves pain and improves function in fibromyalgia syndrome: a randomized, double-blind, placebo-controlled, multicenter clinical trial.

OBJECTIVE: To evaluate the safety and efficacy of sodium oxybate for management of the symptoms of fibromyalgia syndrome (FMS).

METHODS: Patients with FMS (according to the American College of Rheumatology 1990 criteria) were randomized, after discontinuing their prestudy medications for FMS, to receive 4.5 gm or 6 gm of sodium oxybate or matching placebo once per night for 8 weeks. The primary outcome variable (POV) was 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 (PVAS), the Fibromyalgia Impact Questionnaire (FIQ) score, and the Patient Global Impression of Change (PGI-C). A beneficial response rate for the POV composite score was defined as >or=20% improvement in the PVAS and FIQ scores plus a rating of "much better" or "very much better" on the PGI-C. Secondary measures included subjective sleep outcomes (on the Jenkins Scale for Sleep) and quality-of-life measures. The analyses were based on an intent-to-treat (ITT) population.

RESULTS: The ITT population included 188 patients with FMS, 78% of whom completed the trial. Significant benefit was observed with both dosages of sodium oxybate, according to changes in the POV and subjective sleep quality. Improvements in the PVAS score were significantly correlated with sleep outcomes. Sodium oxybate was well tolerated overall; dose-related nausea (<or=28% of patients) and dizziness (<or=18% of patients) tended to resolve with continued therapy.

CONCLUSION: Sodium oxybate therapy was well tolerated and significantly improved the symptoms of FMS. Further study of sodium oxybate as a novel therapeutic option for FMS is warranted.