Parkinson disease (PD) is a chronic progressive neurodegenerative disorder that affects >1 million people in the United States. PD causes both motor and nonmotor disturbances; common symptoms include resting tremor, rigidity, and bradykinesia. The current goals of treatment are to slow disease progression and to reduce disability without inducing long-term complications. The classes of agents currently approved for the treatment of PD include levodopa/carbidopa, dopamine agonists, catechol-O-methyl-transferase (COMT) inhibitors, monoamine-oxidase type B (MAO-B) inhibitors, anticholinergics, and agents/ combinations from other drug classes. Newer agents, such as rasagiline and rotigotine, offer additional treatment options to healthcare professionals. Despite these advances in the treatment of PD symptoms, current therapies do not prevent neuron degeneration. Research into new treatments is focused on neuroprotective drugs, new dopamine agonists, and nondopaminergic agents; the goal of these investigative..