Medications and Surgery in Parkinson’s Disease

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Treating
Parkinson’s Disease

Parkinson’s disease symptoms respond well to the correct medication. As the disease progresses, however, your medicine may become less effective and your doctor may adjust the dosage or prescribe a different drug or drug combination.

We recommend that you keep a log of your symptoms to make it easier for your doctor to measure your progress. Do not stop taking your medicine or change the dosage without your doctor’s approval, since you could cause serious complications or make your symptoms worse. Also, make sure to tell your doctor about all other medicines that you are taking, including over–the–counter drugs, because they may interact with your prescribed anti–Parkinson’s drug. For example, antacids may interfere with L–dopa, a commonly prescribed anti–Parkinson’s medicine.

Parkinson’s disease is progressive. Although there is no reliable cure, your quality of life can be improved. The first line of offense is medication, although surgery may be necessary in some advanced cases.

We have provided an overview of the different treatments for Parkinson’s disease. We hope you will find it helpful as you consult with your doctor and medical team.

Levodopa or L–dopa Is the Most Common Parkinson’s Treatment

The gold standard of Parkinson’s treatment, Levodopa or L–dopa, relieves the problems of body rigidity and slowed movement. It may also help balance and reduce tremors. L–dopa is the precursor to dopamine, a substance that is in short supply in Parkinson’s disease patients. Dopamine cannot be given directly because it cannot cross through the body’s blood/brain barrier. L–dopa, however, can cross this barrier and change to dopamine.

L–dopa is often combined with carbidopa, a substance that allows more L–dopa to be converted into dopamine in the brain. Sinemet® is the brand name for the combination of L–dopa and carbidopa.

Side effects of L–dopa include nausea, dizziness, and vomiting. Depending upon your individual body chemistry, you may or may not experience all these side effects. Combining L–dopa with carbidopa sometimes lessens these problems, since less L–dopa is required.

Eventually, L–dopa or L–dopa/carbidopa becomes less effective. Patients may experience jerky, involuntary movements called dyskinesias and “on–off” periods when L–dopa will suddenly start or stop working. Combining L–dopa or Sinemet® with other drugs may prove helpful in reducing these unwanted movement difficulties.

Dopamine Agonists

Dopamine agonists copy the effects of dopamine by acting directly on dopamine receptors in the brain. They include bromocriptine (Parlodel®), pramipexole (Mirapex®) and ropinirole (Requip®). These drugs may be used in combination with L–dopa. They help reduce the amount of L–dopa necessary for smooth functioning and may therefore partly counteract its long–term side effects. Some doctors believe that dopamine agonists should be used instead of L–dopa as the initial Parkinson’s treatment, especially for early onset Parkinson’s disease.

Parlodel® and Permax® are synthetic derivatives of ergot, a plant alkaloid produced by a type of fungus. They help restore movement functions. Mirapex® and Requip® are non–ergot compounds that have been used to treat both early and advanced Parkinson’s disease. Side effects of dopamine agonists may include nausea and vomiting, sleepiness, insomnia, dizziness, hallucinations, confusion, and occasional low blood pressure.

Anticholinergic drugs

Anticholinergic drugs decrease the activity of the neurotransmitter, acetylcholine. Acetylcholine interacts with dopamine and effects dopamine levels.

Anticholinergic drugs include trihexyphenidyl hydrochloride (Artane®) and benztropine mesylate (Cogentin®). They are used to treat mild forms of Parkinson’s disease, or in combination with L–dopa. They are more effective in reducing tremors than L–dopa (2002 Report of the American Academy of Neurology). Side effects can include dry mouth, blurred vision, constipation, urinary problems, and confusion.

COMT Inhibitors

COMT inhibitors work by blocking COMT (catechol O–methyltransferase), an enzyme which breaks down L–dopa before it can make dopamine. Tolcapone (Tasmar®) and entacapone (Comtan®) are examples of COMT inhibitors. They are taken with L–dopa/carbidopa, and allow that combination to work longer.

Tasmar® is reserved for patients who do not have severe movement problems and who cannot take or benefit from other available treatments. The government has issued warnings about Tasmar® because it may cause serious liver damage and even death (Tasmar®, FDA summary; FDA Talk paper, November 1998). Doctors have been advised to monitor and test Tasmar® patients for liver problems. If you are taking Tasmar®, you should tell your doctor immediately if you experience signs of liver disease such as yellowing of your skin and eyes, fatigue, and loss of appetite.

Other Parkinson’s Medications

Originally used to treat respiratory infections, amantadine (Symmetrel®) may be used to relieve symptoms of Parkinson’s disease, including “on–off” periods when Sinemet® stops working. Although its side effects are less pronounced than other Parkinson’s disease medications, Symmetrel® may only have a mild effect on Parkinson’s symptoms, according to a recent report (2002 Report of the American Academy of Neurology). Seligiline (Eldepryl®) provides mild relief of symptoms and may possibly delay the need for L–dopa. It also is an antidepressant. More research may be done on both of these drugs.

The Role of Surgery in Parkinson’s Treatment

Surgery may be helpful when medications no longer work. A “pallidotomy” is an operation that involves destruction of the part of the brain called the globus pallidus, which controls some movements. A patient with Parkinson’s disease has an overactive globus pallidus. This is the result of producing less dopamine. Destroying part of the globus pallidus may help restore normal movements and reduce dyskinesias and tremors.

The usual procedure is a unilateral pallidotomy, performed on only one–half of the structure. Patients under 70 years of age, without dementia, obtain the best results.

In some cases, a pallidotomy does not help reduce Parkinson’s disease symptoms. Risks include infection and stroke, but these are not common. For more details see Pallidotomy for Parkinson’s Disease and an article in the Journal of Neurology.

Deep brain stimulation (DBS) is a procedure that delivers high frequency, electrical stimulation into a target area of the brain. An electrode tip is placed in the brain regions known as the thalamus, globus pallidus, or subthalamus. The patient can turn the stimulation on or off using a special control device.

Unlike a pallidotomy, DBS is reversible, because the stimulation system may be removed. DBS has been known to improve tremors, slowed movements, rigidity, and dyskinesia. Risks include initial infection when the electrodes are implanted. The exact reason why DBS helps patients is unknown. See Deep Cell Stimulation in Parkinson’s Disease.

Clinical Trials

A clinical trial is a research study using volunteers. The goal is to find cures or treatments for diseases such as Parkinson’s disease or other serious health conditions. Researchers must conduct animal or laboratory studies that produce positive results before they try a new procedure or drug on human subjects in a clinical trial. A typical Parkinson’s disease clinical trial determines whether a treatment is safe and effective, the best way to administer a drug, and the proper dosage. Any side effects are observed and noted.

Your doctor or medical center may recommend a particular Parkinson’s clinical trial. You may also read about a clinical trial that is recruiting volunteers through a newspaper or magazine. Some patients actively look for clinical trials. If you are in the later category, you may want to consult the web sites listed below, then discuss what you found with your doctor and medical team.

Researchers around the world are investigating the causes and treatment of Parkinson’s disease. In the United States, the Udall Parkinson’s Disease Research Act of 1997 increased the funding for fighting the disease and established Parkinson’s disease divisions in medical centers throughout the country. Both private and government foundations are active in the search for a complete cure, giving us renewed hope for a future without Parkinson’s disease.