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Objective:Assess the efficacy of duloxetine 60/120 mg (N = 162) once daily compared with placebo (N = 168) in the treatment of patients with fibromyalgia, during six months of treatment.Methods:This was a phase-III, randomized, double-blind, placebo-controlled, parallel-group study assessing the efficacy and safety of duloxetine.Results:There were no significant differences between treatment groups on the co-primary efficacy outcome measures, change in the Brief Pain Inventory (BPI) average pain severity from baseline to endpoint (P = 0.053) and the Patient’s Global Impressions of Improvement (PGI-I) at endpoint (P = 0.073). Duloxetine-treated patients improved significantly more than placebo-treated patients on the Fibromyalgia Impact Questionnaire pain score, BPI least pain score and average interference score, Clinical Global Impressions of Severity scale, area under the curve of pain relief, Multidimensional Fatigue Inventory mental fatigue dimension, Beck Depression Inventory-II total score, and 36-item Short Form Health Survey mental component summary and mental health score. Nausea was the most common treatment-emergent adverse event in the duloxetine group. Overall discontinuation rates were similar between groups.Conclusions:Although duloxetine 60/120 mg/day failed to demonstrate significant improvement over placebo on the co-primary outcome measures, in this supportive study, duloxetine demonstrated significant improvement compared with placebo on numerous secondary measures.

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Objective. To estimate the minimum clinically important difference (MCID) for several pain measures obtained from the Brief Pain Inventory (BPI) for patients with fibromyalgia. Methods. Data were pooled across 12-week treatment periods from 4 randomized, double-blind, placebo-controlled studies designed to evaluate the safety and efficacy of duloxetine for the treatment of fibromyalgia. Each study enrolled subjects with American College of Rheumatology-defined fibromyalgia who presented with moderate to severe pain. The MCIDs for the BPI average pain item score and the BPI severity score (the mean of the BPI pain scale values: right now, average, least, and worst) were estimated by anchoring against the Patient's Global Impressions of Improvement scale. Results. The anchor-based MCIDs for the BPI average pain item and severity scores were 2.1 and 2.2 points, respectively. These MCIDs correspond to 32.3% and 34.2% reductions from baseline in scores. Conclusion. In these analyses, the MCIDs for several pain measures obtained from the BPI were similar (ϳ2 points) and corresponded to a 30 -35% improvement from baseline to end point. These findings may be beneficial for use in designing clinical trials in which the BPI is used to evaluate improvements in pain severity.

Sensory profiles are heterogeneous in neuropathic pain disorders, and subgroups of patients respond differently to treatment. To further explore this, patients in the COMBO-DN study were prospectively assessed by the Neuropathic Pain Symptom Inventory (NPSI) at baseline, after initial 8-week therapy with either duloxetine or pregabalin, and after subsequent 8-week combination/high-dose therapy. Exploratory post hoc cluster analyses were performed to identify and characterize potential subgroups through their scores in the NPSI items. In patients not responding to initial 60 mg/d duloxetine, adding 300 mg/d pregabalin for combination treatment was particularly effective regarding the dimensions pressing pain and evoked pain, whereas maximizing the duloxetine dose to 120 mg/d appeared more beneficial regarding paresthesia/dysesthesia. In contrast, adding 60 mg/d duloxetine to 300 mg/d pregabalin in case of nonresponse to initial pregabalin led to numerically higher decreases in all NPSI dimensions/items compared to maximizing the pregabalin dose to 600 mg/d. Cluster analysis revealed 3 patient clusters (defined by baseline scores for the 10 NPSI sensory items) with different pain profiles, not only in terms of overall pain severity, but also across NPSI items. Mean Brief Pain Inventory average pain improved in all clusters during combination/high-dose therapy. However, in patients with severe pain, the treatment effect showed a trend in favor of high-dose monotherapy, whereas combination therapy appeared to be more beneficial in patients with moderate and mild pain (not significant). These complementary exploratory analyses further endorse the idea that sensory phenotyping might lead to a more stratified treatment and potentially to personalized pain therapy.