Efficacy of duloxetine by prior NSAID use in the treatment of chronic osteoarthritis knee pain: A post hoc subgroup analysis of a randomized, placebo-controlled, phase 3 study in Japan

A previously conducted placebo-controlled, randomized, phase 3 study of 353 Japanese patients with knee osteoarthritis (OA) showed significant improvements for duloxetine vs placebo in pain and health-related quality of life (HRQoL) (ClinicalTrials.gov Identifier: NCT02248480). Reported here are post hoc subgroup analyses evaluating the efficacy of duloxetine according to the pattern of prior nonsteroidal anti-inflammatory drug (NSAID) use.Patients with knee OA pain received once-daily duloxetine or placebo for 14 weeks. Pain was evaluated using the Brief Pain Inventory (BPI) and HRQoL was evaluated using the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC). Patients were divided into four subgroups based on their prior NSAID use: (i) no prior NSAID use; (ii) low-frequency NSAID use (14 days/month); (iii) high-frequency transdermal NSAID use (transdermal NSAIDs only; ≥14 days/month for the 3 months before study entry); and (iv) high-frequency other NSAID use (eg, oral NSAIDs only, both oral and transdermal NSAIDs; ≥14 days/month for the 3 months before study entry).In each of the four prior NSAID use subgroups, there were greater reductions in BPI average pain severity score for duloxetine vs placebo at all timepoints during the 14-week treatment period; the treatment*prior NSAID use interaction was not statistically significant. In each subgroup, the proportion of patients achieving a ≥50% reduction in BPI average pain severity score was higher for duloxetine vs placebo. In each subgroup, there were greater reductions in WOMAC total score for duloxetine vs placebo at all timepoints; the treatment*prior NSAID use interaction was not statistically significant. In each subgroup, there were greater reductions at Week 14 in WOMAC pain, stiffness, physical function, and total scores for duloxetine vs placebo.Duloxetine was consistently effective with respect to pain relief and HRQoL in Japanese patients with knee OA pain, regardless of the pattern of prior NSAID use.