Objectives: To investigate whether comorbid major depressive disorder (MDD) influenced the efficacy and safety of duloxetine in treating fibromyalgia (FM).

Methods: This was a post-hoc analysis using pooled data from 4 double-blind, placebo-controlled studies of patients with American College of Rheumatology-defined primary FM with or without MDD. Patients were randomized to duloxetine [60 or 120 mg/d (N=797)] or placebo (N=535) for approximately 3 months. Efficacy measures included the Brief Pain Inventory average pain score, 17-item Hamilton Depression Rating Scale, Fibromyalgia Impact Questionnaire, and Patient's/Clinician's Global Impressions of Improvement/Severity scales.

Results: At baseline, 26% of patients met diagnostic criteria for MDD. At endpoint (3 mo or last observation), duloxetine showed significantly (P<0.05) greater improvement versus placebo on the Brief Pain Inventory, Fibromyalgia Impact Questionnaire, Patient's Global Impressions of Improvement scale, and Clinician's Global Impressions of Severity scale in patients with and without comorbid MDD. The effect of duloxetine on these efficacy measures was consistent across FM patients with or without MDD (P>0.1 for treatment-by-strata interaction). On the 17-item Hamilton Depression Rating Scale, duloxetine showed significantly (P<0.05) greater improvement versus placebo in patients with comorbid MDD. The safety profile of duloxetine versus placebo with respect to serious adverse events and discontinuation owing to adverse events was similar for FM patients with versus without MDD (P>0.1 treatment-by-strata interaction).

Discussion: Duloxetine was effective in reducing pain and other symptoms in FM patients with and without MDD and demonstrated a similar safety profile for both groups.