Sodium Oxybate Reduces Pain in Patients with Moderate and Severe Fibromyalgia Symptoms

AUSTIN, TXSodium oxybate was shown to be effective in patients with both moderate to severe fibromyalgia symptoms, according to an analysis presented at the American Pain Society’s 30th Annual Scientific Meeting. Sodium oxybate is not currently approved for the treatment of fibromyalgia.

I. Jon Russell, MD, PhD, of the Texas Health Sciences Center, San Antonio, TX, and colleagues from Oregon Health & Science University, Portland, OR, and Jazz Pharmaceuticals, Inc., Palo Alto, CA, analyzed pooled data from two 14-week, Phase 3, double-blind, randomized, placebo-controlled trials to determine the proportions of responders (≥30% reduction on a 0–100mm pain visual analogue scale [VAS]) by moderate (VAS ≥50 to <70) or severe (≥70) pain and by moderate or severe disease, based on clinician global impression of severity (CGI-S) at baseline. A total of 1,121 patients were randomized in the two trials, and were given placebo, sodium oxybate 4.5g or 6g in equal, divided doses at bedtime and 2.5–4 hours later. The data were analyzed by baseline-observation-carried-forward (BOCF) and last-observation-carried-forward (LOCF) methods.

In patients with pain VAS ≥50 to <70, approximately 51% and 54% receiving sodium oxybate 4.5g and 6g, respectively, were responders vs. placebo (29%; P<0.001, LOCF). In patients with pain VAS ≥70, 45% (P=0.013) and 56% (P<0.001), respectively, were responders vs. placebo (33%, LOCF). Subgroup analysis based on CGI-S demonstrated similar efficacy in both dose groups vs. placebo for both the moderately ill/less severe (53% for both doses vs. 35% for placebo; P<0.001, LOCF) and markedly ill/more severe, 41% for sodium oxybate 4.5g (P=0.004) and 57% (P<0.001) for 6 g vs. 25% for placebo(LOCF) groups. BOCF analyses by baseline pain and CGI-S also demonstrated statistically significant efficacy of both sodium oxybate doses vs. placebo (overall P<0.001 for moderately ill/less severe patients and P=0.002 for markedly ill/more severe patinets). The most common adverse events (≥5% in any sodium oxybate treatment group and at least twice the rate of placebo) were nausea, dizziness, vomiting, anxiety, and fatigue.

Dr. Russell et al. concludedthese analyses demonstrate that in patients with fibromyalgia, sodium oxybate demonstrates efficacy for the rduction of pain regardless of whether pain and disease severity were moderate or severe at baseline. Greater proportions of patients having moderate and severe pain, and moderate and severe disease severity achieved ≥30% reduction in pain with sodium oxybate at doses of 4.5g and 6g compared with placebo.