Efficacy and tolerability of flupirtine in sub-acute/chronic musculoskeletal pain - results of a patient level, pooled re-analysis of randomized, double-blind, controlled trials

Introduction: Flupirtine, a non-opioid analgesic without antipyretic or antiphlogistic properties, constitutes a unique class within the group of WHO-I analgesics. First approved in Germany on a national level in 1989, this selective neuronal potassium channel opener evolved rapidly into one of the most preferred analgesics for the treatment of musculoskeletal pain in sonic European countries. However, its use outside Europe was limited due to a discrepancy between the empirical application of the drug and supporting evidence. As a consequence, the German Pain Society commissioned an independent research institute to perform a pooled re-analysis of all available data from randomized controlled trials (including some trial not yet published). Methods: A retrospective pooled analysis of the individual patient data from 8 randomized controlled Phase III - IV clinical trials was carried out which included patients with sub-acute and chronic musculoskeletal pain. The efficacy and tolerability of flupirtine at dosages of 100 400 mg/d were compared to placebo and/or active comparators. Data were pooled by treatment and by subject. The primary endpoint was the average change in pain intensity for the overall maintenance period. Results: A total of 1,046 patients was evaluated for efficacy and 1,095 patients for safety. Based on 3,337 pain assessments, treatment with flupirtine and active comparators resulted in significant reductions in pain intensity compared to baseline beginning from Day 4 (flupirtine) and Day 5 (comparators) and continuing up to the end of the study period as well as during the overall maintenance period (all p < 0.001). Flupirtine prooved to be non-inferior to the active comparators (p < 0.001) but showed a superior tolerability profile with a significantly lower number of patients reporting treatment emergent adverse events (28.6 vs. 39.1%, p < 0.001) and a significantly lower percentage of patients who prematurely discontinued study medication due to these adverse events (7.1 vs. 11.7%, p = 0.013). Limitations: The limitations in the study were confined to those inherent in the retrospective and pooled analysis design. Conclusion: On the basis of this pooled analysis of individual data from 8 controlled clinical trials involving patients suffering from sub-acute/chronic musculoskeletal pain, the efficacy of flupirtine was superior to placebo across its effective and approved dosage range. Flupirtine was at least as active as the active comparators and showed a superior tolerability profile with a significantly lower treatment discontinuation rate.