'No clinically relevant effect': Duloxetine fails to impact chronic osteoarthritis pain
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Adding duloxetine to usual care fails to result in any “clinically relevant effect” in patients with chronic hip or knee osteoarthritis pain, compared with usual care alone, according to data published in Arthritis & Rheumatology.
“Several placebo-controlled trials have examined the efficacy of duloxetine for patients with OA and found effect sizes of 0.4 to 0.5 for pain and 0.6 for disability,” Jacoline J. van den Driest, MD, of Erasmus MC, University Medical Center, in Rotterdam, the Netherlands, and colleagues wrote. “Based on these trials, the Osteoarthritis Research Society International (OARSI) recommends duloxetine for patients with knee OA with depression and/or widespread pain and the American College of Rheumatology (ACR) conditionally recommends duloxetine for OA.
“The effectiveness of duloxetine added to usual care compared to usual care alone in a primary care setting is unknown, while most OA patients are treated in this setting for many years,” they added. “Neither is it known whether the presence of symptoms of centrally sensitized pain alters the response to duloxetine.”
To examine the effectiveness of adding duloxetine (Cymbalta, Eli Lilly & Co.) to usual care among patients with chronic OA pain, as well as assess its cost-effectiveness and whether symptoms of centralized pain alter the drug’s response, Driest and colleagues conducted an open-label, cluster randomized trial. The researchers recruited participants from a total of 231 general practitioners across 110 practices in the southwestern region of the Netherlands.
In all, 132 adults with chronic hip or knee OA pain, who had an insufficient response to paracetamol and NSAIDs, were randomized 1:1 to receive 60 mg of daily duloxetine added to their usual care or usual care alone. Usual care included education, lifestyle advice, diet, physiotherapy and analgesics, with glucocorticoids via intra-articular injection also allowed. Centralized pain was identified based a modified painDETECT score of greater than 12.
The primary outcome was WOMAC pain at 3 months. Driest and colleagues aimed to detect a difference between the groups with a clinically relevant effect of 1.9 points and an effect size of 0.4. Analysis included a linear mixed model with repeated measurements.
The 12-month follow-up was completed by 53 participants in each group.
According to the researchers, there were no differences in WOMAC pain between the groups at 3 months (adjusted difference = –0.58; 95% CI, –1.8 to 0.63) or at 12 months (–0.26; 95% CI, –1.86 to 1.34). The researchers similarly found no effect of duloxetine among the 47% of included participants with symptoms of centralized pain (–0.32; 95% CI, –2.32 to 1.67). However, they concluded that the drug’s impact currently “cannot be ruled out” among this population.
“There was no clinically relevant effect of duloxetine added to usual care compared to usual care alone for chronic OA pain and it should not be implemented,” Driest and colleagues wrote. “For patients with symptoms of centralized pain an effect cannot be ruled out and future research in this subgroup is needed to confirm our results.”
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