Parkinson’s disease is a chronic, progressive neurodegenerative disease that results from the death of certain neurons in an area of the brain that controls movement. These neurons are responsible for producing dopamine, an essential brain signaling chemical, or neurotransmitter, which enables smooth, coordinated movements of both voluntary and involuntary muscles throughout the body. The lack of dopamine in patients with Parkinson’s disease produces characteristic symptoms including tremor at rest, rigidity, impaired movement and balance, as well as significant non-motor symptoms including cognitive impairment and mood disorders, sleep disturbances, fatigue, bowel and bladder dysfunction and in some cases, dementia.
The onset of symptoms and speed of progression of disease differs for each patient. Initially, a patient may have little motor impairment; however, as the disease progresses, motor function and the severity of symptoms gradually worsens until a patient is no longer able to perform normal daily tasks such as eating, bathing and dressing.
According to the National Parkinson’s Foundation, there are over one million people with Parkinson’s disease in the U.S., with 50,000 to 60,000 new patients diagnosed each year.
Current Treatment Approaches and Inherent Limitations
There is no cure or disease modifying treatment currently available for Parkinson’s disease. Current treatment strategies are focused on the management and reduction of the major symptoms of the disease and related disabilities, with treatment becoming less effective over time as the disease progresses. The standard of care regimen for symptomatic treatment of Parkinson’s disease is levodopa, which was the first drug approved specifically for Parkinson’s disease nearly 50 years ago. Levodopa is most often administered orally in combination with a peripheral dopamine decarboxylase inhibitor, usually carbidopa, in order to increase the amount of levodopa that enters the brain and to decrease the frequency of dopamine-related side effects. Such side effects can include nausea, dizziness, and orthostatic hypotension.