A small, open-label, randomized trial of patients with chronic pain from hip and knee osteoarthritis in the Netherlands shows that adding duloxetine to usual care doesn’t significantly improve clinical outcomes.
The results, published on Jan. 6 in Arthritis & Rheumatology, also showed duloxetine did not affect outcomes for a subgroup of patients who had symptoms of centrally sensitized pain, according to Jacoline J. van den Driest, MD, of the department of general practice at Erasmus University Medical Center, Rotterdam, the Netherlands, and colleagues.
The researchers acknowledged their findings contrast with other studies that showed a “small to moderate effect of duloxetine” for patients with chronic pain from hip and knee OA. There was also a higher rate of discontinuation of duloxetine around 3 months in the current trial, compared with previous studies, the authors said, which they attributed to the fact that clinicians were asked to discontinue treatment at 3 months if patients saw no effect or increased side effects.
“This difference in outcome can be due to the fact that we studied the effectiveness of duloxetine in primary care, while the other studies examined the efficacy in placebo-controlled trials in secondary care,” the researchers wrote. Patients in the current trial were also older, had more comorbidities, and had been living with OA symptoms “for a longer time” than patients in other trials, they explained.
“It is known that, in these more ‘real-life’ primary care populations and in effectiveness studies, smaller effects are found than in highly controlled efficacy trials,” they noted.
van den Driest and colleagues evaluated 132 patients with hip or knee OA between January 2016 and February 2019 who were cluster randomized at 66 general practitioner practice sites to receive duloxetine (30 mg/day in the first week, 60 mg/day in the second week and beyond) in addition to usual care that consisted of analgesics, physiotherapy, patient education, diet, and lifestyle advice. Patients were included in the study if they were at least 18 years old, met the American College of Rheumatology criteria for hip or knee OA, and experienced chronic pain for “most days” over 3 months that was not improved through use of NSAIDs or acetaminophen or were unable to use NSAIDs because of contraindications or adverse effects. They were excluded if taking duloxetine was contraindicated for them, if they were taking an antidepressant or neuropathic pain medication, and if they had rheumatoid arthritis or were scheduled for total hip or total knee replacement.
The researchers assessed patients’ Western Ontario McMaster Universities (WOMAC) Osteoarthritis Index pain scores at 3 months, compared with baseline, as a primary outcome, with secondary outcomes of WOMAC pain and function at 1 year, and cost-effectiveness as measured by the EQ-5D-5L. A modified painDETECT questionnaire was also used at baseline to identify a subset of patients with presence of centralized pain, which was defined as a score >12.
At 12 months, 80.3% of patients in both groups completed follow-up. Patient characteristics differed in duloxetine and usual-care groups, with the duloxetine group being younger (63.2 years vs. 65.4 years) and having fewer women (59.1% vs. 75.8%). The duloxetine group also had a lower percentage of patients with knee OA (77.3% vs. 86.4%) and a lower percentage of patients with two or more comorbidities (15.2% vs. 33.2%).
Duloxetine led to a nonsignificant improvement in WOMAC-measured pain at 3 months, compared with usual care (adjusted difference, –0.58; 95% confidence interval, –1.80 to 0.63), and at 12 months (adjusted difference, –0.26; 95% CI, –1.86 to 1.34). Among a subgroup of patients with central sensitization symptoms, there was a nonsignificant improvement in WOMAC-measured pain at 3 months (adjusted difference, –0.32; 95% CI, –2.32 to 1.67) and 12 months (adjusted difference, 1.02; 95% CI, –1.22 to 3.27).
Duloxetine also did not significantly improve WOMAC-measured function at 3 months (adjusted difference, –2.10; 95% CI, –6.39 to 2.20) or 12 months (adjusted difference, –1.79; 95% CI, –7.22 to 3.64).
For other secondary outcomes of quality of life, patient satisfaction, and Outcome Measures in Rheumatology (OMERACT)-Osteoarthritis Research Society International (OARSI) responder criteria, van den Driest and colleagues noted that “none of the differences between the two groups were clinically relevant or statistically significant.”
Some Patients May Likely Still Benefit From Duloxetine
Commenting on the results, Joshua F. Baker, MD, MSCE, associate professor of rheumatology and epidemiology at the University of Pennsylvania and Philadelphia VA Medical Center, said the study by van den Driest and colleagues is pragmatic and demonstrates the ” ‘real-world’ benefits of trying duloxetine” – one of the study’s strengths.
“As we would probably expect, the benefits are small, and somewhat smaller in this setting than what was observed in more standard clinical trials evaluating this question,” he said, noting that the study is limited by a small sample size and loss to follow-up, as well as its open-label design and the fact that most patients stopped treatment during follow-up.
Baker also explained that while patients on average did not have a meaningful effect after taking duloxetine, “that doesn’t mean that the therapy didn’t have a meaningful effect for some people.”
“In fact, though most people didn’t receive a meaningful benefit in this study, some did,” he said. “[A]ccording to these data, treating 8 people would be expected to result in 1 person achieving an [OMERACT-OARSI] response. That’s pretty good for a disease with few things that work.”
Future study of duloxetine should focus on who is most likely to benefit from treatment “since while most probably don’t benefit a lot, some probably do,” he said.
Baker also called attention to the questions surrounding use of antidepressants. “Use of antidepressants has been questioned by some, since the average clinical benefit is low, even for conditions like depression,” he explained. “However, some would argue that even small benefits may be important since there are few things that do work very well, and because a multimodal approach that provides multiple small benefits to patients can add up to a meaningful benefit.”
This study was funded by The Netherlands Organization for Health Research and Development. One author reported receiving grants from The Netherlands Organization for Health Research and Development, the European Union, FOREUM, and the Dutch Arthritis Association, as well as personal fees from OARSI and Pfizer. The other authors reported no relevant financial disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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