This 14-week, phase 3, double-blind, randomized, controlled trial evaluated sodium oxybate (SXB) 4.5 and 6g per night versus placebo in patients with fibromyalgia (FM). SXB is the sodium salt of γ-hydroxybutyrate (GHB). GHB is an endogenous compound, synthesized from γ-aminobutyric acid (GABA) and found broadly in the central nervous system and body. Among 548 randomized patients, a ≥30% reduction in pain was experienced by 54.2% and 58.5% of patients treated with SXB 4.5 and 6g, respectively, versus 35.2% for placebo with a 100-mm Visual Analog Scale (VAS) (P<0.001 for both comparisons). Relative to placebo, both SXB doses significantly reduced fatigue (with a 100-mm VAS; P<0.001) and sleep disturbance (with the Jenkins Sleep Scale; P<0.001), and resulted in significant improvements in function as measured by the FM Impact Questionnaire (P=0.003 and P=0.001 for 4.5 and 6 g per night, respectively). On the Short-Form 36 Health Survey, SXB-related improvement was significant on the Physical, but not the Mental, Component Scale. The proportion of patients who reported a global improvement of "much" or "very much" better on the Patient Global Impression of Change was significantly greater in both SXB groups versus placebo (P<0.001). Headache, nausea, dizziness, vomiting, diarrhea, anxiety, and sinusitis were the most commonly reported adverse events, with an incidence at least twice that of placebo. These results expand the evidence from previous clinical trials suggesting that SXB is effective and safe in FM.
BackgroundFibromyalgia is characterised by chronic musculoskeletal pain and multiple symptoms including fatigue, multidimensional function impairment, sleep disturbance and tenderness. Along with pain and fatigue, non-restorative sleep is a core symptom of fibromyalgia. Sodium oxybate (SXB) is thought to reduce non-restorative sleep abnormalities. This study evaluated effects of SXB on fibromyalgia-related pain and other symptoms.Methods573 patients with fibromyalgia according to 1990 American College of Rheumatology criteria were enrolled at 108 centres in eight countries. Subjects were randomly assigned to placebo, SXB 4.5 g/night or SXB 6 g/night. The primary efficacy endpoint was the proportion of subjects with ≥30% reduction in pain visual analogue scale from baseline to treatment end. Other efficacy assessments included function, sleep quality, effect of sleep on function, fatigue, tenderness, health-related quality of life and subject's impression of change in overall wellbeing.ResultsSignificant improvements in pain, sleep and other symptoms associated with fibromyalgia were seen in SXB treated subjects compared with placebo. The proportion of subjects with ≥30% pain reduction was 42.0% for SXB4.5 g/night (p=0.002) and 51.4% for SXB6 g/night (p<0.001) versus 26.8% for placebo. Quality of sleep (Jenkins sleep scale) improved by 20% for SXB4.5 g/night (p≤0.001) and 25% for SXB6 g/night (p≤0.001) versus 0.5% for placebo. Adverse events with an incidence ≥5% and twice placebo were nausea, dizziness, vomiting, insomnia, anxiety, somnolence, fatigue, muscle spasms and peripheral oedema.ConclusionThese results, combined with findings from previous phase 2 and 3 studies, provide supportive evidence that SXB therapy affordsimportant benefits across multiple symptoms in subjects with fibromyalgia.
Scientific inveStigAtionSStudy objectives: This study reviewed the cumulative postmarketing and clinical safety experience with sodium oxybate (Xyrem ® ), a treatment approved for cataplexy and excessive daytime sleepiness in narcolepsy. Study objectives were to investigate the occurrence of abuse/misuse of sodium oxybate since first market introduction in 2002, classify cases using DSM-IV criteria for substance abuse and dependence, and describe specific characteristics of these cases. Methods: We retrospectively reviewed postmarketing spontaneous adverse event (AE) reports from 15 countries for all cases containing reporting terminology related to abuse/misuse to determine its occurrence. All death cases independent of causality were reviewed to identify associated risk factors. Results: Approximately 26,000 patients worldwide received sodium oxybate from first market introduction in 2002 through March 2008. Of those 26,000 patients, 0.2% reported ≥ 1 of the events studied. These included 10 cases (0.039%) meeting DSM-IV abuse criteria, 4 cases (0.016%) meeting DSM-IV dependence criteria, 8 cases (0.031%, in-cluding 3 of the previous 4) with withdrawal symptoms reported after discontinuation of sodium oxybate, 2 confirmed cases (0.008%) of sodium oxybate-facilitated sexual assault, 8 cases (0.031%) of overdose with suicidal intent, 21 deaths (0.08%) in patients receiving sodium oxybate treatment with 1 death known to be related to sodium oxybate, and 3 cases (0.01%) of traffic accidents involving drivers taking sodium oxybate. During this period, approximately 600,000 bottles of sodium oxybate were distributed, and 5 incidents (0.0009%) of diversion were reported. conclusion: Cumulative postmarketing and clinical experience indicates a very low risk of abuse/misuse of sodium oxybate.
There remains a dearth of validated measures for assessing EDS and cataplexy in children and adolescents with narcolepsy. The need for these measures may be filled by modification or adaptation of existing adult measures; a daily cataplexy diary and the ESS may be readily modified to make them child-friendly with regard to wording and settings, but should still undergo psychometric validation.
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