Parkinson's disease, abbreviated PD, is a debilitating movement disorder characterized by tremors, loss of balance and loss of muscle movement. Roughly 500,000 Americans have PD, although the exact total may be higher, due to undiagnosed cases, according to the National Institute of Neurological Disorders and Stroke. Several common treatments for PD involve stimulating the dopamine pathway in the brain. Most of these treatments are available only by prescription and should be taken only under the supervision of a qualified health-care provider.
Parkinson's Disease and Dopamine
Dopamine is a neurotransmitter produced by the brain that carries signals from one part of the brain to another. Dopamine levels and PD are intricately linked, and one of the major causes of PD appears to be the abnormal death of brain cells that produce dopamine. A crucial role of dopamine is coordinating brain signals that control muscle movement and activity. Without dopamine, the brain cannot properly control muscle movements throughout the body, leading to the symptoms of PD, says the University of Maryland Medical Center.
Levadopa
Unfortunately, patients with PD cannot simply take dopamine pills to replenish dopamine levels. The brain is protected by the "blood-brain barrier" which prevents many large chemicals and molecules from flowing into the brain in the bloodstream. Instead, PD patients often take a chemical precursor of dopamine called levadopa, or L-dopa, which can cross the blood-brain barrier and is then converted into dopamine in the brain, according to New York University Langone Medical Center.
Dopamine Agonists
Levadopa treatment is often successful during the early stages of PD. Over time, however, levadopa often begins to lose effectiveness and cause side effects. When this happens, many doctors recommend supplementing or replacing levadopa with other medications known as dopamine agonists. These medications often mimic the activity of dopamine by stimulating the receptors in the brain that normally recognize dopamine, according to an article published in the January 2006 issue of the journal "Expert Review of Neurotherapeutics."
Side Effects
Both levadopa and dopamine agonists can cause disruptive side effects. Initially, levadopa and dopamine agonists often cause nausea, vomiting, low blood pressure, restlessness and sudden sleep onset. More severe side effects, including hallucinations and psychosis, may also occur. Over time, many people taking levadopa experience involuntary movements, including twisting, twitching and writhing, a side effect known as dyskinesis, says the National Institute of Neurological Disorders and Stroke. In rare cases, long-term use of dopamine agonists can cause compulsive behaviors, including compulsive shopping, gambling and hypersexuality.
References
- National Institute of Neurological Disorders and Stroke; Parkinson's Disease: Hope Through Research; January 2006
- University of Maryland Medical Center: Parkinson's Disease
- New York University Langone Medical Center; Parkinson's Disease; February 2011
- "Expert Review of Neurotherapeutics"; Dopamine Agonists in the Treatment of Parkinson's Disease; Ubaldo Bonuccelli and Nicola Pavese; Janurary 2006
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