Treatments available include medication, non-drug treatment, and surgery.
Medication Treatment Options:
There are six major groups of drugs used to treat Parkinson's disease.
Levodopa is the chemical precursor to the neurotransmitter dopamine that is lacking in patients with Parkinson's disease. Taking levodopa can help correct this deficiency. Levodopa is converted to dopamine in the brain. While levodopa does not eliminate Parkinson's disease symptoms, it can provide significant relief and remains the gold standard for treatment. Sometimes levodopa is combined with carbidopa in a single pill to help levodopa work better and to decrease some side effects, such as nausea. This side effect can also be prevented by taking the medication 30 minutes after meals. As Parkinson's disease progresses, patients may experience side effects from the drug such as confusion, vivid dreams, hallucinations, or positional lightheadedness. Unfortunately, as Parkinson's disease progresses, patients must often increase the amount and frequency of their levodopa doses, as the drug's effectiveness lessens. Some patients may experience dyskinesias (uncontrolled drug-induced movements) as they increase their dose. Deep brain stimulation surgery can help control the unpredictable fluctuations and dyskinesias that occur with levodopa use in advanced Parkinson's disease.
Dopamine agonists are drugs that have a similar effect as dopamine by acting on the same brain receptors. While they are less effective then levodopa, they are also less prone to some side effects and they last longer than levodopa, providing a more steady effect.
The greatest advantage of dopamine agonists is their ability to allow patients to avoid using levodopa early in the course of Parkinson's disease and thus delay the onset of dyskinesias and fluctuations caused by long-term levodopa use. This makes them a preferred choice for the initial treatment of younger patients with relatively mild symptoms. Side effects include nausea and confusion (especially in elderly patients). Some patients have developed compulsive behaviors while on these drugs. These behaviors cease when the drug is stopped. Caution should be exercised in the use of dopamine agonists in elderly or cognitively impaired patients.
Three dopamine agonists are available in the US for Parkinson's disease treatment:
- Bromocriptine (Parlodel)
- Ropinirole (Requip)
- Pramipexole (Mirapex)
Eldepryl (Selegiline, Deprenyl) and rasagiline are MAO-B antagonists. MAO-B is an enzyme responsible for the breakdown of dopamine. Inhibiting this enzyme prevents the destruction of dopamine, thus increasing the amount of dopamine available in the brain. These drugs are less effective as compared to levodopa or dopamine agonists. The DATATOP study showed that Selegiline may also be a neuro-protective agent, possibly slowing the progression of early Parkinson's disease. In our practice, we use selegiline in early, uncomplicated Parkinson's disease.
COMT is another enzyme that breaks down dopamine in the brain. There are two of these enzyme inhibitors available in the US: tolcapone (Tasmar) and entacapone (Comtan). Tasmar is rarely used due to the risk of liver toxicity. These drugs are useful in those Parkinson's disease patients whose medication seems to be wearing off rapidly and the levodopa benefit does not last from one dose to the next. These drugs have side effects that are very similar to those of levodopa except Comtan may also cause diarrhea.
These drugs act by blocking the action of the neurotransmitter acetylcholine in the brain. They are most effective in patients with severe tremor as the most significant symptom of Parkinson's disease. The most common anticholinergic drugs used are Artane (trihexyphenidyl) and Cogentin (benztropine). Unfortunately, these medications have a high propensity to cause cognitive side effects, especially in the elderly. Other common side effects include visual blurring, dryness of the mouth and urinary retention. Anticholinergics may not be used in patients with glaucoma.
Amantadine (Symmetrel) is an antiviral drug that was incidentally found to be effective in Parkinson's disease as well. It is used in patients with early stage Parkinson's disease and who have severe tremor. Amantadine is also been shown to be of benefit in patients with advanced, fluctuating Parkinson's disease with dyskinesias.
Of Note: Antidepressants do not affect Parkinson's disease symptoms per se, but can be quite effective in the management of Parkinson's disease patients with depression, a common consequence of disease. Serotonin reuptake inhibitors, like Paxil or Zoloft are usually effective and well tolerated. Tricyclic antidepressants, like Elavil (amitriptyline) in low doses, can be quite useful for the management of Parkinson's-related pain.
These treatments do not rely on medications:
- Patient and family support, and support groups
- Physical therapy
- Occupational therapy
- Speech and swallowing therapy
- Nutritional consultation
- Resources: associations, products, assistive devices
- Alternative interventions: yoga, tai chi, acupuncture, relaxation, visualization
Surgical Treatment Options:
Ablative or Lesioning Surgery
Lesions are made in specific anatomical locations in the brain.
Deep Brain Stimulation
A permanent stimulating electrode is placed in an area of the brain known as the subthalamic nucleus. An implanted neurostimulator (similar to a pacemaker) sends high-frequency electrical pulses through the electrode to stimulate the brain and suppress Parkinson's disease symptoms. For more information, please see the patient's guide to deep brain stimulation surgery.
Many studies are underway investigating the effectiveness of various gene therapy and stem cell methods for curing Parkinson's disease.