An open-label, long-term, phase III extension trial of duloxetine in Japanese patients with fibromyalgia

<p><i>Objectives</i>: We aimed to evaluate the long-term safety and efficacy of duloxetine 60 mg in Japanese patients with fibromyalgia enrolled from a preceding randomized, placebo-controlled, phase III duloxetine trial.</p> <p><i>Methods</i>: This was a long-term, open-label extension study. Patients received oral duloxetine once daily at a dose of 20 mg for 1 week, followed by 40 mg for 1 week, and then 60 mg for 48 weeks. The primary outcome was the frequency of adverse events (AEs) and adverse drug reactions (ADRs) of duloxetine. Efficacy and health outcomes were assessed.</p> <p><i>Results</i>: In total, 149 patients were enrolled from the preceding study. The median length of treatment was 364.0 days. The incidence of AEs and ADRs was 92.6 and 63.8%, respectively. ADRs occurring at an incidence of ≥5% were somnolence, constipation, nausea, weight increase, thirst, and malaise. The proportion of patients with mild, moderate, and severe AEs was 80.5, 10.1, and 2.0%. There were no serious treatment-related AEs in this study. The Brief Pain Inventory average pain score improved at all time-points compared with baseline (mean change ± standard deviation at Week 50 was −1.31 ± 1.70).</p> <p><i>Conclusions</i>: Duloxetine was safe and effective in the long-term treatment of Japanese patients with fibromyalgia.