Parkinson's disease (PD) is a chronic and progressive degenerative disorder of the central nervous system characterized by tremor, rigidity, slowness of movement (bradykinesia) and postural abnormalities. The cause is unknown, but the pathology shows that dopamine is profoundly reduced in the basal ganglia of patients with PD. When dopamine is replenished by the administration of levodopa, most of the symptoms of parkinsonism are reduced significantly. Levodopa is considered to be the most reliable and effective symptomatic drug treatment for keeping patients autonomous and functionally independent for as long as possible.