Effectiveness of pharmacologic treatment for dysphagia in Parkinson’s disease: a narrative review

The effectiveness of pharmacological treatment on dysphagia in Parkinson’s disease (PD) is debatable. We reviewed the literature for analyzing the effect of pharmacological treatment on the improvement of dysphagia in PD patients. We searched the PubMed database for papers published before June 21, 2020, that evaluated the effect of pharmacologic treatments for improving dysphagia in patients with PD. The following inclusion criteria were applied for the selection of articles: 1) studies performed on patients with dysphagia due to PD, 2) studies where pharmacologic treatment was applied for improvement of dysphagia, and 3) those where follow-up evaluation was performed after the treatment. The primary literature search yielded 415 relevant papers. After reading their titles and abstracts and assessing their eligibility based on the full-text articles, we finally included nine studies in this review. In five previous studies, the positive effects of dopaminergic drugs on dysphagia were reported, whereas two showed no significant positive results. The remaining two studies showed equivocal results. We found that dopaminergic drugs have some potential to improve dysphagia in patients with PD. However, studies with high-quality evidence are lacking. For the clear elucidation of the effect of dopaminergic drugs on dysphagia in patients with PD, randomized controlled trials with large cohorts and detailed analyses should be conducted in the future.