Efficacy and Safety of Duloxetine in Patients with Chronic Low Back Pain Who Used versus Did Not Use Concomitant Nonsteroidal Anti-Inflammatory Drugs or Acetaminophen: A Post Hoc Pooled Analysis of 2 Randomized, Placebo-Controlled Trials

This subgroup analysis assessed the efficacy of duloxetine in patients with chronic low back pain (CLBP) who did or did not use concomitant nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen (APAP). Data were pooled from two 13-week randomized trials in patients with CLBP who were stratified according to NSAID/APAP use at baseline: duloxetine NSAID/APAP user ( n = 137), placebo NSAID/APAP user ( n = 82), duloxetine NSAID/APAP nonuser ( n = 206), and placebo NSAID/APAP nonuser ( n = 156). NSAID/APAP users were those patients who took NSAID/APAP for at least 14 days per month during 3 months prior to study entry. An analysis of covariance model that included therapy, study, baseline NSAID/APAP use (yes/no), and therapy-by-NSAID/APAP subgroup interaction was used to assess the efficacy. The treatment-by-NSAID/APAP use interaction was not statistically significant ( P = 0.31) suggesting no substantial evidence of differential efficacy for duloxetine over placebo on pain reduction or improvement in physical function between concomitant NSAID/APAP users and non-users.