Effect of Rasagiline on Balance in Parkinson's Disease as Measured by Computerized Posturography

Inclusion Criteria: 1. 18 years old or above 2. Clinical diagnosis of Parkinson disease by verified by movement disorders expert at the initial study visit with at least two cardinal signs of the disease (rest tremor, bradykinesia, rigidity, and postural instability). 3. For the monotherapy arm, patients must not be on amantadine, dopamine agonists, or levodopa. For the adjuvant therapy arm: Patients must be on a stable dose of their current medication for treatment of Parkinson disease which may include any combination of the following: amantadine, trihexiphenydil, dopamine agonist, and/or levodopa. 4. Patients may continue their stable dose of tricyclic, selective serotonin reuptake inhibitor, or serotonin norepinephrine reuptake inhibitor if they are on these medications at randomization. Exclusion Criteria: 1. Catechol-O-Methyltransferase (COMT) inhibitor therapy use 30 days prior to start of study (both study arms). 2. Dopamine receptor blocker use (such as quetiapine) one week prior to taking study drug 3. For both monotherapy and adjuvant therapy arms: use of MAO inhibitor therapy including selegiline or rasagiline within 30 days prior to taking study drug and first posturography evaluation.