In Patients with Fibromyalgia, Flexible Doses of Duloxetine Provide Greater Pain Reduction vs Placebo

BALTIMORE, Md.—Patients with fibromyalgia reported feeling much better and experienced greater pain reduction with flexible doses of duloxetine (60-120 mg/day) compared with placebo, investigators reported during The American Pain Society's 29th Annual Scientific Meeting. Results from the first fibromyalgia duloxetine trial allowing dose adjustment based on clinical response and tolerability, as is typically done in clinical practice, also found that patients had improvement in sleep, stiffness, and functioning.

Daniel J. Clauw, MD, and colleagues randomized outpatients aged 18 to 65 years with fibromyalgia and ≥4 score on the Brief Pain Inventory (BPI) to either duloxetine (n=263) or placebo (n=267) over 24 weeks. Primary end point was change in symptoms at week 12 using the Patient Global Impression of Improvement (PGI-I). Secondary end points included average pain severity on the BPI, sleep and stiffness (using patient-rated Likert scales), and results from the SF-36, a multi-purpose, short-form health survey.

Duloxetine treatment was initiated at 30 mg/day for 1 week; the dose was then increased to 60 mg/day. Double-blind dose-adjustments were allowed at week 4 (to 90 mg/day) and week 8 (to 120 mg/day or dose reduction). Mean patient global impression of illness severity score at baseline was 3.8 (moderately ill). Increasing the dose of duloxetine in patients who had an inadequate pain response was associated with further pain reduction and suggests that duloxetine 90 mg/day may be an appropriate intermediate dose for some patients.

At end point, patients in the duloxetine group had mean PGI-I scores of 2.8 compared with 3.4 for placebo (P<0.001). Significantly more patients who received duloxetine (57%) reported feeling “much” or “very much” better (PGI-I score ≤2) than those receiving placebo (32.2%; P<0.001). Treatment with duloxetine resulted in significantly greater between-treatment improvement in BPI average pain severity, sleep and stiffness, and all measures on the SF-36 (except role-physical) compared with placebo. Please see corresponding PowerPoint slides for more information.

About half of patients received higher doses of duloxetine: 23.6%, 90 mg, and 24.3%, 120 mg. Nausea, headache, constipation, dry mouth, dizziness, diarrhea, and hyperhidrosis occurred in at least 5% of patients treated with duloxetine and significantly more frequently than in those receiving placebo.