Duloxetine 60 mg once-daily in the treatment of painful physical symptoms in patients with major depressive disorder

BACKGROUND: While emotional symptoms such as depressed mood and loss of interest have traditionally been considered to constitute the core symptoms of major depressive disorder (MDD), the prevalence and importance of painful physical symptoms such as back pain, abdominal pain, and musculoskeletal pain is becoming increasingly appreciated. Antidepressants possessing dual serotonin/norepinephrine (5-HT/NE) reuptake inhibition may demonstrate greater efficacy in the alleviation of pain. The efficacy of duloxetine, a balanced and potent dual reuptake inhibitor of 5-HT and NE, was evaluated within a cohort of depressed patients with associated painful physical symptoms. METHODS: In this multicenter, double-blind, placebo-controlled study, patients meeting DSM-IV criteria for MDD were randomized to receive placebo (N=141) or duloxetine 60 mg QD (N=141). Patients were required to have a 17-item Hamilton Rating Scale for Depression (HAMD17) total score 15, a Clinical Global Impression of Severity (CGI-S) score 4, and a Brief Pain Inventory (BPI) Average Pain score 2 at baseline. The primary efficacy measure was the BPI Average Pain score, while secondary measures included other BPI items, the HAMD17 total score, CGI-S, the Patient Global Impression of Improvement (PGI-I) scale, Visual Analog Scales (VAS) for pain, and the Symptom Questionnaire, Somatic Subscale (SQSS). Safety was evaluated by recording treatment-emergent adverse events (spontaneously reported), vital signs, and laboratory analytes. RESULTS: Mean changes in BPI Average Pain for duloxetine- and placebo-treated patients differed significantly at most visits, but only approached significance at endpoint p=0.066. For the main effect of treatment (pooling all visits), significant advantages for duloxetine-treated patients were found in 10 of 11 assessed BPI pain severity and pain interference items, in addition to VAS overall pain and back pain. Mean changes in pain measures for duloxetine-treated patients corresponded to improvements of 25-50%, compared with 19-39% for placebo. Mean changes at endpoint in depression rating scales (HAMD17, CGI-S, PGI-I) did not differ significantly between duloxetine and placebo treatment groups due to unusually high placebo response. The magnitude of placebo treatment effects (as measured by HAMD17 total score and Maier subscale) was significantly smaller in patients with 1 previous depressive episode, compared to those patients with no previous episodes. In patients with 1 previous depressive episode the advantage of duloxetine over placebo was similar to previous studies. Rates of discontinuation due to adverse events were 14.2% vs. 2.1% for duloxetine and placebo, respectively p<0.001. Treatment-emergent adverse events reported at a significantly higher rate by duloxetine-treated patients included nausea, dry mouth, fatigue, and decreased appetite. CONCLUSIONS: In this study, duloxetine (60 mg QD) was shown to be an effective treatment for the painful physical symptoms which are frequently associated with depression. Improvements in pain severity occurred independently of changes in depressive symptom severity.