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.

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.