Parkinson disease (PD) is the second most common neurodegenerative disease after Alzheimer disease. The prevalence of PD is increasing rapidly and is expected to double by 2040, to the extent that it has been called a Parkinson pandemic.1 The global burden of PD has also doubled in the last 20 years.2 The economic impact of PD has been substantially and consistently increasing, specifically with regard to the advanced stage of the disease.3 All of these factors indicate an urgent need for disease-modifying and ultimately curative and preventive therapies. Such therapies do not currently exist despite substantial efforts. On the positive side, PD has a large number of symptomatic therapies available for improvement of motor disability. Although levodopa has and remains the criterion standard, current oral preparations have the disadvantage of being associated with motor fluctuations and dyskinesia. As a result, levodopa adjunctive therapies have been a major target of drug development. All major classes of adjunctive therapies, such as dopamine agonists, catechol-O-methyltransferase (COMT) inhibitors, and monoamine oxidase type B (MAO-B) inhibitors, have been found to be efficacious in reducing off time compared with placebo in well-designed studies and have been reported to be clinically useful based on an expert evidence-based systematic review.4 However, there is paucity of data on direct head-to-head comparison of the comparative efficacy, impact for quality of life, and health economic outcomes of different classes of adjunctive therapies.5