Early Pain Reduction With Duloxetine May Predict Long-Term Efficacy in Knee Osteoarthritis

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The study included 353 patients diagnosed with knee osteoarthritis, based on criteria by the American College of Rheumatology.
The study included 353 patients diagnosed with knee osteoarthritis, based on criteria by the American College of Rheumatology.

The following article is part of conference coverage from the IASP 2018 conference in Boston, Massachusetts. Clinical Pain Advisor's staff will be reporting breaking news associated with research conducted by leading experts in pain medicine. Check back for the latest news from IASP 2018.

Patients with osteoarthritis and knee pain who experience an early reduction in pain intensity when treated with duloxetine may experience long-term improvements in pain and quality of life from continued duloxetine intervention, according to a study to be presented at the 2018 World Congress on Pain, held September 12-16 in Boston, Massachusetts.

This post-hoc analysis of a randomized placebo-controlled double-blind Japanese trial sought to assess whether early pain reduction or early treatment-related adverse events were associated with long-term efficacy of duloxetine in patients with osteoarthritic knee pain.

Analysis was performed on data reported by the Japanese trial, which evaluated the safety and efficacy of duloxetine intervention to treat patients with osteoarthritis and knee pain. The study included 353 patients diagnosed with knee osteoarthritis, based on criteria by the American College of Rheumatology, with an average pain severity score >4 on the Brief Pain Inventory scale. The participants were randomly assigned 1:1 to receive duloxetine (60 mg/day), or placebo for 14 weeks. Outcome measures were assessed at weeks 2, 4, 6, 10, and 14. Patients treated with duloxetine were grouped according to treatment efficacy at week 4 (ie, pain reduction ≥30%, 10%-30%, or <10%), or according to safety outcomes by week 2 (with or without treatment-related adverse events).

The 93 participants who received duloxetine and experienced ≥30% pain reduction at week 4 were found to have significant reductions in pain severity scores and quality of life scores. In both groups with study participants experiencing <10% (n=33) and 10 to 30% (n=45) reduction in pain at week 4, no improvements were recorded at most observational points. A total of 52 patients experienced early treatment-related adverse events of special interest, vs 125 patients who did not. Regardless of safety outcomes, participants receiving duloxetine showed significant reductions in pain scores and improvements in quality of life scores compared with patients receiving placebo.

“A reduction in pain intensity during early treatment might predict which patients with [osteoarthritis] pain are most likely to respond to [duloxetine] with a clinically significant reduction in pain, and [quality of life] improvements,” concluded the study authors. “Improved [quality of life] scores were notably consistent with patients' subjective improvement.”

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Reference

Itoh N, Tsuji T, Ishida M, et al. Response to duloxetine in patients with knee pain due to osteoarthritis: an exploratory post-hoc analysis of a Japanese phase 3 randomized study.Presented at: the World Congress on Pain 2018; September 12-16, 2018; Boston, MA. Poster 63838.WEBSITE

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