Maintenance of Effect of Duloxetine in Patients with Chronic Low Back Pain: A 41-week Uncontrolled, Dose-blinded Study

Objective. To assess the maintenance of the effect of duloxetine in the treatment of chronic low back pain. Methods. Patients (N = 181) with chronic low back pain entered a 41-week extension phase after completing a 13-week placebo-controlled treatment phase. The maintenance of the effect was assessed in patients taking duloxetine 60/120 mg/day who met the response criteria (>= 30% reduction in Brief Pain Inventory average pain) at the end of the placebo-controlled phase. In addition, physical function was evaluated using the Roland-Morris Disability Questionnaire, the Clinical Global Impressions-Severity of Illness, and the Brief Pain Inventory Pain Severity and Interference ratings. Quality of life, safety, and tolerability outcomes were also assessed. Finally, placebo-treated patients were switched to duloxetine 60 mg/day at the beginning of the extension phase and their response to treatment is also reported. Results. Initial responders to duloxetine treatment demonstrated further significant improvement (within-group) in pain, physical function, and quality of life. Significant within-group improvements were also observed in the extension phase for placebo-treated patients who were switched to duloxetine. Duloxetine was well tolerated with no new safety findings reported. Conclusions. In this study, the analgesic effect of duloxetine in patients with chronic low back pain was not only maintained for 41 weeks, but additional statistically significant improvement in pain and function was observed.