To determine response with duloxetine versus placebo in patients with osteoarthritis (OA) of the knee using the Outcome Measures in Rheumatoid Arthritis Clinical Trials-Osteoarthritis Research Society International (OMERACT-OARSI) responder index and other clinically relevant outcomes including minimal clinically important improvement (MCII) and patient acceptable symptom state (PASS) for pain and function.
Data were pooled from two 13-week, randomized, double-blind, placebo-controlled trials comparing duloxetine 60 to 120 mg/day with placebo in patients with symptomatic OA of the knee. Treatment response was determined according to the OMERACT-OARSI responder index, ≥ 30% pain reduction, ≥ 50% pain reduction, and MCII and PASS for pain and function. (ClinicalTrials.gov identifiers NCT00433290 and NCT00408421)
Duloxetine-treated patients were 33% more likely to experience an OMERACT-OARSI response than placebo-treated patients [p < 0.001, number needed to treat (NNT) = 6]. A significantly greater percentage of duloxetine-treated patients, compared with placebo-treated patients, reported ≥ 30% improvement in pain from baseline to endpoint (p < 0.001, NNT = 5) and ≥ 50% improvement in pain relative to baseline (p < 0.001, NNT = 7). The duloxetine-treated patients were also more likely to fulfill MCII criteria for pain (p < 0.001, NNT = 6) and function (p < 0.001, NNT = 7), and to achieve PASS for pain (p < 0.001, NNT = 6) and function (p = 0.009, NNT = 9). More duloxetine-treated patients compared with placebo-treated patients experienced ≥ 1 treatment-emergent adverse event (p = 0.003, number needed to harm = 8).
Significantly more patients receiving duloxetine than placebo achieved an OMERACT-OARSI response, improvements in pain and function exceeding the level accepted as MCII, and reached PASS. Results support the clinical relevance of outcomes of prior duloxetine studies in symptomatic OA of the knee.