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Open Access Highly Accessed Research article

Long-term tolerability and maintenance of therapeutic response to sodium oxybate in an open-label extension study in patients with fibromyalgia

Michael Spaeth16*, Cayetano Alegre2, Serge Perrot3, Youyu Grace Wang4, Diane R Guinta4, Sarah Alvarez-Horine4, Irwin Jon Russell5 and the Sodium Oxybate Fibromyalgia Study Group

Author Affiliations

1 Rheumatologische Schwerpunktpraxis, Bahnhofstrasse 95, 82166 Graefelfing, Munich, Germany

2 Institut Universitari Dexeus, Carrer Sabino de Arana 5, 08028 Barcelona, Spain

3 Service de Médecine Interne et Consultation de la Douleur, Hôpital Dieu, Université Paris, Descartes, INSERM U 987, 1 Place du Parvis Notre Dame, 75004 Paris, France

4 Jazz Pharmaceuticals, Inc, 3180 Porter Drive, Palo Alto, CA 94304, USA

5 Department of Medicine, University of Texas Health Science Center at San Antonio, 7434 Floyd Curl Drive, San Antonio, TX 78229, USA

6 Leitender Arzt Rheumatologie, Spital Linth, 8730 Uznach, Switzerland

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Arthritis Research & Therapy 2013, 15:R185  doi:10.1186/ar4375

Published: 11 November 2013

Abstract

Introduction

The long-term safety and therapeutic response of sodium oxybate (SXB) in fibromyalgia syndrome (FM) patients were assessed for a combined period of up to 1 year in a prospective, multicenter, open-label, extension study in patients completing 1 of 2 phase 3 randomized, double-blind, controlled, 14-week trials that examined the efficacy and safety of SXB 4.5 g, SXB 6 g, and placebo for treatment of FM.

Methods

This extension study comprised an additional 38 weeks of treatment and was carried out at 130 clinical sites in 7 countries. Initial entry criteria for the previous 2 double-blind clinical trials required that patients aged ≥ 18 years met the American College of Rheumatology 1990 criteria for FM, had a body mass index (BMI) < 40 kg/m2, and had a score ≥ 50 on a 100-mm pain visual analog scale (VAS) at baseline. All patients began treatment in the extension study with SXB 4.5 g/night (administered in 2 equally divided doses) for at least 1 week, followed by possible serial 1.5 g/night dose increases to 9 g/night (maximum) or reductions to 4.5 g/night (minimum).

Results

Of the 560 FM patients enrolled in this extension study, 319 (57.0%) completed the study. The main reason for early discontinuation was adverse events (AEs; 23.0% of patients). Patients were primarily middle-aged (mean 46.9 ± 10.8 years), female (91.1%), white (91.4%), with a mean duration of FM symptoms of 9.9 ± 8.7 years. Serious AEs were experienced by 3.6% of patients. The most frequently reported AEs (incidence ≥ 5% at any dose or overall) were nausea, headache, dizziness, nasopharyngitis, vomiting, sinusitis, diarrhea, anxiety, insomnia, influenza, somnolence, upper respiratory tract infection, muscle spasms, urinary tract infection, and gastroenteritis viral. Maintenance of SXB therapeutic response was demonstrated with continued improvement from controlled-study baseline in pain VAS, Fibromyalgia Impact Questionnaire (FIQ) total scores, and other measures. Responder analyses showed that 68.8% of patients achieved ≥ 30% reduction in pain VAS and 69.7% achieved ≥ 30% reduction in FIQ total score at study endpoint.

Conclusions

The long-term safety profile of SXB in FM patients was similar to that in the previously reported controlled clinical trials. Improvement in pain and other FM clinical domains was maintained during long-term use.

Trial registration

ClinicalTrials.gov NCT00423605.