Effects of soybean ingestion on pharmacokinetics of levodopa and motor symptoms of Parkinson's disease — In relation to the effects of Mucuna pruriens

Abstract Mucuna pruriens is a levodopa-containing legume and its favorable effects on motor complications in Parkinson disease patients have been reported. The aim of this study was to investigate the effects of another legume, soybeans, on the pharmacokinetics and metabolism of levodopa. Seven parkinsonian patients with the wearing-off phenomenon and dyskinesia and five healthy volunteers participated in this study. We conducted a crossover study of the clinical effects on the participants before and after taking either levodopa (100 mg)/carbidopa (10 mg) only (LD/CD) or levodopa/carbidopa with 11 g of ground soybeans (LD/CD/soy). Parkinsonism and dyskinesia before and after ingestion of these substances were evaluated using UPDRS partIII, the modified Abnormal Involuntary Movement Scale (mAIMS) and a self-rating scale. The concentrations of plasma levodopa and its major metabolites were measured by high-performance liquid chromatography. Clinical assessment and blood sampling were conducted before and three hours after the ingestion of ground soybeans. When the patients took LD/CD/soy, they had a significantly longer on-period ( p  = 0.028) and a lower mAIMS score ( p