Effect of duloxetine in patients with fibromyalgia: tiredness subgroups

Laurence A Bradley,Fujun Wang,Irwin J Russell,Madelaine M Wohlreich,Harvey Moldofsky,Amy S Chappell,Robert Bennett,Deborah N D'Souza

doi:10.1186/ar3081

Abstract

IntroductionThis study tested the hypothesis that baseline ratings of fatigue/tiredness would be negatively associated with the efficacy of duloxetine on measures of pain and functional ability in patients with fibromyalgia.MethodsA post hoc analysis of pooled data from 4 double-blind, placebo-controlled studies of duloxetine in fibromyalgia was performed. The fibromyalgia impact questionnaire (FIQ) tiredness item score (0 to 10 scale) was used to define tiredness subgroups. Patients were stratified into 3 subgroups: mild (0 to 3), moderate (4 to 6), and severe (7 to 10) tiredness. Analysis of covariance models and logistic regressions were used to test treatment-by-tiredness subgroup interactions.ResultsData from the first 3 months are included in this post hoc analysis (duloxetine N = 797, placebo N = 535). At baseline, the distribution of tiredness severity in the duloxetine and placebo groups respectively was 3.64% and 3.75% mild, 16.71% and 15.57% moderate, and 79.65% and 80.68% severe. Rates of clinically significant (≥30% and ≥50%) improvement in brief pain inventory (BPI) average pain were similar across the tiredness subgroups. Tiredness severity at baseline was not negatively associated with the effects of duloxetine on patients' reports of functional ability using the FIQ total score, FIQ measures of physical impairment, interference with work, pain, stiffness, and depression and the medical outcomes study short form-36 (SF-36).ConclusionsStudies of duloxetine in fibromyalgia have demonstrated clinically significant improvements in pain and functional ability (FIQ, SF-36). This post hoc analysis of data shows that the efficacy of duloxetine among patients with fibromyalgia does not vary as a function of baseline ratings of fatigue/tiredness.

Highlights

This study tested the hypothesis that baseline ratings of fatigue/tiredness would be negatively associated with the efficacy of duloxetine on measures of pain and functional ability in patients with fibromyalgia
Efficacy measures by tiredness subgroups Brief pain inventory Within the severe subgroup, there was a significant difference between the duloxetine and placebo groups (P < 0.001) in the number of patients with 30% or greater and 50% or greater reductions in the brief pain inventory (BPI) average pain response (Figure 1)
For the BPI average pain score, within the severe subgroup there was a significant difference (P < 0.001) in the mean change from baseline to endpoint between the duloxetine and placebo groups (Table 2)

Summary

Introduction

This study tested the hypothesis that baseline ratings of fatigue/tiredness would be negatively associated with the efficacy of duloxetine on measures of pain and functional ability in patients with fibromyalgia. Additional symptoms that often accompany fibromyalgia are tiredness or fatigue, depressed mood, sleep disturbance, and headache [2,3]. Preclinical models of central sensitization suggest that duloxetine is efficacious in the treatment of patients with persistent/ chronic pain. Duloxetine is efficacious in the treatment of the painful physical symptoms associated with depression and the pain associated with diabetic neuropathy in nondepressed patients [6,7]. The results of four placebocontrolled clinical trials of duloxetine in the treatment of fibromyalgia have been previously reported [8,9,10,11]

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Discussion

Conclusion