Flexible Dosed Duloxetine in the Treatment of Fibromyalgia: A Randomized, Double-blind, Placebo-controlled Trial

Objective. To investigate the efficacy of flexible dose duloxetine 60-120 mg/day on changes in fibromyalgia (FM) symptoms assessed by the Patient Global Impression of Improvement (PGI-I) scale. Methods. Outpatients a 18 years of age who met American College of Rheumatology criteria for FM, and had >= 4 score on the Brief Pain Inventory (BPI) average pain item, were randomized to duloxetine (n = 263) or placebo (n = 267) for 24 week double-blind treatment (primary endpoint at Week 12). Key secondary measures included BPI average pain severity, patient-rated scales assessing mood, anxiety, pain, sleep, and stiffness, Clinical Global Impression of Severity (CGI-S), Multidimensional Fatigue Inventory, Cognitive and Physical Functioning Questionnaire, Beck Depression Inventory (BDI), Beck Anxiety Inventory, and Medical Outcome Study Short-Form Health Survey (SF-36). Results. At Week 12, duloxetine-treated patients reported significantly greater global improvement with mean PGI-I scores of 2.8 compared to 3.4 in the placebo group (p <0.001). Significantly more duloxetine- versus placebo-treated patients (57% vs 32%; p < 0.001) reported feeling much or very much better (PGI-I score <= 2). There was significantly greater improvement with duloxetine versus placebo treatment in BPI average pain severity, mood (including BDI total), anxiety (patient-rated only), stiffness. CGI-S, fatigue, all SF-36 domains (except role-physical and physical component summary), and being less bothered by pain or sleep difficulties. Treatment-emergent adverse events occurring significantly more frequently with duloxetine included: nausea, headache, constipation, dry mouth, dizziness, diarrhea, and hyperhidrosis. Conclusion. Treatment with duloxetine 60, 90, and 120 mg/day was associated with feeling much better, pain reduction, being less bothered by sleep difficulties, and improvement in mood, stiffness, fatigue and functioning. (Clinical trial registry NCT00673452). (First Release Sept 15 2010; J Rheumatol 2010;37:2578-86; doi:3899/jrheum.100365)