Efficacy of duloxetine in patients with knee osteoarthritis or chronic low back pain with early pain reduction: An exploratory post-hoc analysis of Japanese phase 3, 1-year extension studies.

Abstract Background Two previous phase 3, double-blind, randomized, placebo-controlled trials showed that duloxetine 60 mg/day for 14 weeks significantly improved pain and quality of life in Japanese patients with knee osteoarthritis or chronic low back pain. In their open-label extension studies, these improvements were maintained for ≥48 weeks. This post-hoc analysis assessed the relationship between initial response to duloxetine and long-term pain reduction and quality of life in patients with knee osteoarthritis or chronic low back pain. Methods Patients (knee osteoarthritis: N = 43; chronic low back pain: N = 41) were subdivided based on extent of pain reduction from baseline to Week 4 of duloxetine (≥30%, 10–30%, or Results Mean change from baseline in Brief Pain Inventory-Severity was greater in patients with ≥30% early pain reduction than in patients with Conclusions These results suggest that patients with knee osteoarthritis who respond well to duloxetine in the first month might experience sustained, long-term pain relief with generally greater quality-of-life improvement than patients with poor initial response. Patients with chronic low back pain who had strong initial response may experience a greater long-term pain relief, but not greater quality-of-life improvement, than patients with poor initial response.