A Single-Blind, Placebo Run-in Study of Duloxetine for Activity-Limiting Osteoarthritis Pain

Osteoarthritis pain is a significant problem for our aging population. Antidepressants that are serotonin-norepinephrine reuptake inhibitors are effective for other forms of chronic pain and may provide a new treatment option for osteoarthritis pain. We performed a single-blind, placebo run-in trial of 60 to 90 mg of duloxetine in 25 subjects with activity-limiting osteoarthritis pain. Each subject received 2 weeks of placebo followed by 10 weeks of duloxetine. The primary outcome was reduction in average pain intensity between 2 and 12 weeks for subjects completing the trial. Average pain on the Brief Pain Inventory (BPI) was 5.7 at baseline, 4.8 after the 2-week placebo run-in, and 3.5 at 12 weeks for the 17 patients completing the trial (28% decrease between 2 and 12 weeks, P = .122). Eight of 15 study completers; who had nonmissing BPI results (53%) reported at least 30% pain reduction between weeks 2 and 12. The Western Ontario McMaster Osteoarthritis Index (WOMAC) pain score at baseline was 2.3, 1.8 after 2 weeks, and 1.3 after 12 weeks (30% decrease between 2 and 12 weeks, P = .018). Ten of 17 patients (59%) reported at least 30% pain relief between weeks 2 and 12 on the WOMAC. Significant improvements in self-reported physical and role function were reported but observed physical function did not improve. Perspective: Duloxetine did not significantly reduce pain intensity on the BPI but did improve pain intensity and self-reported function on the WOMAC. Duloxetine warrants further investigation as a novel treatment for osteoarthritis pain. (c) 2009 by the American Pain Society