Comparison of the Analgesic Effects of a Fixed-Dose Combination of Orphenadrine and Diclofenac (Neodolpasse®) with its Single Active Ingredients Diclofenac and Orphenadrine: A Placebo-Controlled Study Using Laser-Induced Somatosensory-Evoked Potentials from Capsaicin-Induced Hyperalgesic Human Skin


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Abstract

ObjectiveThe aim of this study was to investigate the analgesic efficacy of Neodolpasse®, a fixed-dose combination of orphenadrine and diclofenac, compared with those of its single active ingredients in a human pain model.MethodsThe study was designed as a randomised, double-blind, placebo-controlled, four-period crossover study. Twenty-four healthy female and male subjects received single infusions of Neodolpasse®, orphenadrine, diclofenac or saline solution over 60 minutes. Infusions were separated by a 1-week washout period. Neurogenic inflammation and hyperalgesia were induced by topical occlusive application of a 1% capsaicin solution for 30 minutes on defined skin areas on the back. The pain response to CO2 laser pulses applied to the capsaicin-pretreated skin was measured by event-related vertex EEG recordings. This allowed us to study the influence of a single infusion on the central P2- and peripheral N1-components of laser-induced somatosensory-evoked potentials (LSEP) as a measure of pain response.ResultsAlthough none of the active treatments had a significant effect on the peripheral N1-component, all active treatments reduced the P2-component of the LSEP, reflecting central/spinal analgesic (anti-hyperalgesic) effects. These effects were statistically significant for orphenadrine (p < 0.0001) and for the combination of orphenadrine and diclofenac (p < 0.0013). The single ingredient diclofenac reduced the P2-component by a value just below clinical relevance (p < 0.0848).ConclusionThis study demonstrated the efficacy of Neodolpasse® in a human pain model. The observed effect was mainly caused by central mechanisms and was found to be superior for the fixed-dose combination of orphenadrine and diclofenac compared with the individual ingredients. Both components contributed to the effect of the combination in an additive fashion, which can be explained by the different molecular mechanisms of action of each drug.

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