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Editor's comment: In October 2010, the FDA turned down Jazz Pharmaceuticals request for approval of sodium oxybate for the treatment of fibromyalgia, citing safety concerns. They expressed particular concerns about the potential for abuse or misuse of the medication.
Sodium oxybate is currently approved for the treatment of excessive daytime sleepiness and cataplexy (the sudden loss of muscle tone) in adult patients with narcolepsy. It's use is monitored by an extremely stringent safety plan – an even more restrictive plan than is used for opioids. Sodium oxybate is classified as a Schedule III drug and its distribution is restricted through the Patient Success Program. It can only be purchased from one central, mail-order pharmacy and patients are first required to read a letter and brochure as well as watch a video about the medication.
One of the reasons the FDA has such serious concerns is likely because sodium oxybate, also known as gamma-hydroxybutyrate (GHB), is known to have been used as a date rape drug in the past. In an effort to address the FDA's concerns, Jazz Pharmaceuticals is conducting additional studies on the safety and efficacy of sodium oxybate for FM. This study looked at the long-term effectiveness and tolerability of the drug.
Long-term tolerability and maintenance of therapeutic response to sodium oxybate in an open-label extension study in patients with fibromyalgia.
By Michael Spaeth, et al.
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.
Source: Arthritis Research & Therapy, November 11, 2013. By Michael Spaeth, Cayetano Alegre, Serge Perrot, Youyu Grace Wang, Diane R Guinta, Sarah Alvarez-Horine, Irwin Jon Russell and the Sodium Oxybate Fibromyalgia Study Group.