Combined Efficacy of Systemically Acting Diclofenac Sodium Patch and Alpha-2-Delta Calcium Channel Ligand in Chronic Low Back Pain: Subanalysis of a Phase III Study

INTRODUCTION: Chronic low back pain often comprises mixed pain types and involves multiple factors. Therefore, we hypothesized that the systemic transdermal formulation of diclofenac sodium (DF systemic patch), which is effective for nociceptive pain, and an α2δ Ca(2+) channel ligand, which is effective for neuropathic pain, would have additive effects in the treatment of chronic low back pain. METHODS: From among participants in a randomized, double-blind, placebo-controlled study of DF systemic patch (75 or 150 mg) applied once daily for 2 weeks in patients with chronic low back pain, we performed a subpopulation analysis of those who were concomitantly treated with an α2δ Ca(2+) channel ligand during the study period. The efficacy endpoint was pain intensity score on a visual analog scale (VAS). RESULTS: The difference (95% confidence interval) in the least square mean pain VAS score between patients in the 150-mg combination group, who were treated with 150-mg DF systemic patch and an α2δ Ca(2+) channel ligand (n = 11), and those in the non-combination group, who were treated with placebo patch and α2δ Ca(2+) channel ligand (n = 22), was − 15.09 mm (− 26.45, − 3.73). Because the upper limit of the 95% confidence interval was less than zero, this result indicates that the pain VAS score improved more in the 150-mg combination group than in the non-combination group (placebo group). CONCLUSIONS: The combination of the DF systemic patch and an α2δ Ca(2+) channel ligand may be more effective than α2δ Ca(2+) channel ligand monotherapy for controlling chronic low back pain. Trial registration numbers: JPRN-JapicCTI-205134 and jRCT2080225040.