Add-on duloxetine exerts null effect on chronic osteoarthritis pain

Adding duloxetine to usual care does not appear to produce significant relief from chronic osteoarthritis (OA) pain as compared with usual care alone, a study has found.

The study included 132 patients with chronic OA pain of hip or knee and who had insufficient response to paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs). They were randomized to receive usual care alone (n=66) or with added duloxetine 60 mg/day (n=66).

Researchers determined the presence of centralized pain using a modified painDETECT score >12. They assigned WOMAC pain (0–20) at 3 months as the primary efficacy outcome. A difference between the groups of 1.9 points (effect size 0.4) was deemed a clinically relevant effect.

Most patients had knee OA (77.3 percent in duloxetine group and 86.4 percent in the usual care group), and 40 percent of the patients had symptoms of centralized pain. Patients with symptoms of centralized pain had higher scores on WOMAC pain.

Compared with the usual care group, the duloxetine group was slightly younger (63.2 years vs 65.4 years), less likely to be women (59.1 percent vs 75.8 percent), and had fewer comorbidities (≥2 comorbidities: 15.2 percent vs 33.2 percent).

There were no differences in WOMAC pain at 3 months (adjusted difference, –0.58, 95 percent confidence interval [CI], –1.80 to 0.63) or at 12 months (adjusted difference, –0.26, 95 percent CI, –1.86 to 1.34).

Results were consistent for the subgroup of patients with symptoms of centralized pain, with duloxetine having no profound effect on WOMAC pain (adjusted difference, –0.32, 95 percent CI, –2.32 to 1.67).

More studies are needed to confirm the role of add-on duloxetine in patients with symptoms of centralized pain.