Efficacy of cyclo-oxygenase-2 inhibition by etoricoxib and naproxen on the axial manifestations of ankylosing spondylitis in the presence of peripheral arthritis

Objective: The combined efficacy of selective and non-selective cyclo-oxygenase-2 (COX-2) inhibition on the axial manifestations of ankylosing spondylitis ( AS) in the presence or absence of chronic peripheral arthritis was evaluated. Methods: In a post hoc subgroup analysis of a 6 week, randomised, double blind, placebo controlled trial, 387 patients with active axial AS were randomised to receive etoricoxib 90 mg or 120 mg once a day, naproxen 500 mg twice daily, or placebo. Randomisation was stratified by the presence or absence of chronic peripheral arthritis. The primary outcome measure was the time weighted average change from baseline of spine pain intensity. Efficacy data from the three groups receiving active treatment (the NSAID/COX-2 inhibitor group) were combined to improve precision. An analysis of covariance model was used to evaluate the effect of peripheral disease on treatment response. Results: 93 patients were allocated to receive placebo and 294 to active treatment ( naproxen or etoricoxib). The combined NSAID/COX-2 inhibitor group had a significant treatment response compared with the placebo group for all efficacy measures, both in patients with and without peripheral arthritis. A significantly greater difference in mean patient assessment of spine pain was found between active and placebo treatments in patients without compared with those with peripheral arthritis (p = 0.005; -32.5 mm v -17.0 mm, respectively). Similar differences, although not statistically significant, were seen for other end points. Conclusion: NSAIDs and COX-2 inhibitors have a clinically relevant symptomatic effect on axial AS irrespective of the presence of peripheral arthritis. In this exploratory analysis spinal improvement appeared to be greater in patients without peripheral disease.