Clinical Outcomes after Onset of Mirogabalin-Related Adverse Drug Reactions in Patients with Lumbar Spinal Stenosis: Post Hoc Analysis of the MiroTAS Study

INTRODUCTION: The MiroTAS study demonstrated the pain-relieving effect and safety of mirogabalin in patients with lumbar spinal stenosis (LSS); however, whether mirogabalin-related adverse drug reactions (mrADRs) affect clinical courses, treatment continuation, or adherence remained unknown. We examined recovery outcomes and treatment status following mrADR onset and whether the analgesic effects of mirogabalin correlated with LSS and leg pain durations. METHODS: This post hoc analysis of the 12-week, randomized controlled MiroTAS study summarized mrADRs (dizziness, somnolence, peripheral edema, and edema) by severity and outcome. Spearman's rank correlations between leg pain changes and duration of LSS and leg pain were examined. RESULTS: Data from 214 patients in the modified intention-to-treat set (mirogabalin add-on: 110; nonsteroidal anti-inflammatory drugs alone: 104) and 216 in the safety analysis set (110 and 106 patients, respectively) were analyzed. Regarding mrADRs, 27/33 dizziness, 25/35 somnolence, 3/6 peripheral edema, and 2/2 edema events recovered or improved. Median times to recovery for dizziness and somnolence were 8.0 and 33.5 days, respectively. Recovery or improvement of dizziness and somnolence occurred in most patients even without dose modification, with a higher proportion of recovery following dose reduction. Most events with moderate dizziness or somnolence (80.0% and 85.7%, respectively) recovered or improved. In the mirogabalin add-on group, Spearman's rank correlation coefficients showed weak positive correlations between change in visual analogue scale (VAS) score for leg pain from baseline to week 12 and LSS duration (P = 0.0269) and no correlation between leg pain duration and change in VAS score. CONCLUSIONS: Our data suggest that dizziness and somnolence are generally manageable under careful monitoring, with most events recovered or improved after onset. The analgesic effect of mirogabalin was weakly associated with LSS duration and not associated with leg pain duration. However, this was a post hoc analysis; given the limited sample size and statistical power, further research is needed. CLINICAL TRIAL REGISTRATION: Japan Registry of Clinical Trials (jRCTs021200007).