The objective of this study is to evaluate the acute effects of alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) receptor blockade on the severity of parkinsonian signs and levodopa-associated motor response complications in patients with Parkinson's disease. In a controlled proof-of-principle clinical trial, efficacy will be assessed through the use of validated motor function scales. Safety will be monitored by means of frequent clinical evaluations and laboratory tests.