Patients with fibromyalgia and comorbid depression had significant improvement in both conditions when treated with duloxetine (Cymbalta), according to pooled data from four clinical trials.
The magnitude of improvement in pain was consistent across all severity levels of depression.
Conversely, patient mood improved to a similar extent across the range of pain severity.
Analysis of treatment effect showed that 60% to 70% of the benefit for pain and mood resulted from a direct effect of the drug.
The remaining 30% to 40% of improvement arose from an indirect effect.
Improvement in pain and improvement in major depressive disorder are positively correlated.
Improvement in pain reflected greater direct treatment effect with an indirect effect of improved mood, indicating that the improvement seen with duloxetine in fibromyalgia is not solely a mood effect. Improvement in mood was found to reflect a greater direct treatment effect, with an indirect effect of pain improvement.
These data support the independent analgesic properties of duloxetine in the treatment of fibromyalgia.”
As many as a third of patients with fibromyalgia have comorbid major depression, and as many as 70% have a history of major depression.
The association between the two conditions is complicated by the fact that the pain can obscure the depression and lead to underdiagnosis and undertreatment.
Major depression can intensify as pain interferes with daily activities, and comorbid depression can lead to increased pain complaints, intensity, and duration among patients with fibromyalgia.
Four placebo-controlled clinical trials of duloxetine in patients with fibromyalgia; limited the analysis to patients who had comorbid major depression at enrollment and who received 60 to 120 mg of duloxetine.
The study involved 350 patients with fibromyalgia and comorbid depression
147 randomized to placebo, and 203 to duloxetine.
Baseline characteristics included a median Hamilton depression (HAMD) score of 15 and a Brief Pain Inventory (BPI) average of 6 to 7.
The analysis showed that about half of the patients with a HAMD score above or below the median had ≥30% improvement in pain score.
35% to 40% of patients treated with duloxetine had ≥50% improvement in pain score whether they had a low (HAMD <15) or high (HAMD ≥15) depression scores.
All of the differences from placebo were statistically significant (P<0.05).
Patients' depression improvement by baseline pain severity did not differ significantly between patients treated with duloxetine or placebo.
About 35% to 40% of duloxetine patients met depression response criteria, regardless of baseline pain severity.
About 25% to 30% of placebo-treated patients also met response criteria for depression.
Analysis showed that 68.7% of pain improvement was attributable to a direct treatment effect of duloxetine and 31.3% to an indirect effect on major depression.
A direct treatment effect of duloxetine accounted for 59.9% of mood improvement, and the remaining 40.1% of improvement was related to the drug's effect on pain.
Explain to patients that this study showed that a drug used to treat fibromyalgia has a direct effect on both pain and major depression.
Note that this study was published as an abstract and presented at a conference.
These data and conclusions should be considered preliminary until published in a peer-reviewed journal