Long-term Efficacy of Safinamide on Parkinson's Disease Chronic Pain

Introduction: Chronic pain is an important yet overlooked non-motor symptom of Parkinson's disease (PD), caused by an imbalance of the dopaminergic and glutamatergic systems. Safinamide has a multimodal mechanism of action, dopaminergic (reversible MAO-B inhibition) and non-dopaminergic (modulation of the abnormal glutamate release), that might be beneficial for both motor and non-motor symptoms. Objectives: To investigate the long-term (2-year) efficacy of safinamide on PD chronic pain and to confirm the positive effects observed after 6 months of treatment. Methods: This is a post hoc analysis of the data from the 2-year study 018, focused on the reduction of concomitant pain treatments and on the scores of pain-related items of the Parkinson's disease quality of life questionnaire (PDQ-39). Results: Safinamide, compared with placebo, significantly improved the PDQ-39 items 37 ("painful cramps or spasm," p = 0.0074) and 39 ("unpleasantly hot or cold," p = 0.0209) and significantly reduced the number of concomitant pain treatments by 26.2% (p = 0.005). A significantly greater proportion of patients in the safinamide group was not using pain drugs after 2 years of treatment (p = 0.0478). Conclusions: The positive effects of safinamide on PD chronic pain were maintained in the long term. Further investigations are desirable to confirm their clinical relevance. Funding: Zambon SpA.