On treatment days, patients will have a brief medical examination before receiving the drug and will then be monitored for side effects for about 6 to 8 hours after taking the drug. At the beginning of weeks 2 and 5, the levodopa infusions will be repeated at the previously determined optimum rate. Throughout the study, parkinsonism symptoms, dyskinesias and depression will be evaluated. Blood and urine samples will be collected each week for standard safety tests, and blood will also be drawn periodically to measure NS2330 levels.