Parkinson's Disease - Treatment
There is no cure for Parkinson's disease. One drug, selegiline (trade name Eldepryl) may slow the destruction of SN brain cells. However, there are a number of treatments for the symptoms of PD.
Exercise, Nutrition, and Physical Therapy
Regular, moderate exercise can improve motor (muscular) control. It improves a person's circulation and appetite and frees up stiff muscles. A physical therapist can help a patient design an exercise program for his or her special needs.
Good nutrition is also important. PD patients often lose interest in food. They may simply lose their appetite, or they may have nausea from drugs they are taking for treatment. Also, as their bodies begin to move more slowly, they may become irritated by how long it takes to eat. Food may digest slowly as well, causing the person to feel full much of the day.
These problems can be partially solved by including more fiber in a person's diet. Soft foods also go down more easily and are digested more quickly. Certain types of drugs can also increase the movement of food through the digestive system.
There is currently no evidence that vitamins, minerals, or other nutritional supplements have any effect on the symptoms of PD.
Researchers have discovered a number of drugs that can help relieve the symptoms of Parkinson's disease. The effectiveness of the drugs depends on many factors. These factors include the patient's body chemistry, the rate at which the disease is progressing, and the length of time the drug has been used. Each PD drug also has side effects. In some cases, those side effects may limit the use of a drug by some patients.
There are presently five classes of drugs used to treat Parkinson's disease.
DRUGS THAT REPLACE DOPAMINE. The symptoms of the disease develop because SN brain cells do not produce enough dopamine. One solution, then, would be to give dopamine to the brain.
The problem with this solution is that the body's blood-brain barrier (BBB) gets in the way. It stops certain toxins and chemicals from entering the brain. In most places in the body substances can pass easily in and out of the blood vessels. This is how the cells of the body get the things they need to function properly. In the BBB, the walls of the blood vessels are much less permeable (open to penetration). The blood-brain barrier is very important because it protects the brain from harmful chemicals and helps maintain a safe, stable environment for sensitive brain tissues. But sometimes helpful chemicals are also kept from entering the brain.
The BBB doesn't allow neurotransmitters or hormones from elsewhere in the body to enter the brain. Dopamine, the chemical needed by Parkinson's patients, is a neurotransmitter. This is a problem for doctors. A person cannot be treated for Parkinson's by being given a pill or an injection of dopamine. The chemical in the pill or injection cannot get through the blood-brain barrier into the brain.
One solution is to "fool" the blood-brain barrier. A patient can be given a drug that looks to the blood-brain barrier like a material it should let through. Researchers have had some success attaching medicines to elements that can pass through the BBB.
In the case of Parkinson's doctors found that they could inject the body with levodopa or L-dopa, a substance that the BBB lets pass into the brain and then turns into dopamine. L-dopa treatments often work for five years or longer. Then the drug begins to lose its effectiveness. It may also begin to produce side effects that are as bad as the symptoms of PD itself.
ENZYME INHIBITORS. Dopamine does not stay in the brain forever. Instead, it is attacked by other chemicals that break it down into other substances. These chemicals are known as enzymes.
Another way to relieve the symptoms of PD, then, is to prevent enzymes from acting on dopamine—that is, to inhibit them from breaking it down. If the enzymes are inhibited, more dopamine will remain in the brain. The drugs given to PD patients often contain L-dopa and one or more enzyme inhibitors.
DOPAMINE AGONISTS. A dopamine agonist is a drug that acts in the brain in much the same way that dopamine does. Patients with Parkinson's disease can take dopamine agonists to make up for missing dopamine. Like other drugs used to treat PD, dopamine agonists can have serious side effects, including confusion and hallucinations at higher doses.
ANTICHOLINERGIC DRUGS. Dopamine is only one of many neurotransmitters in the brain. Brain function depends on a balance of all neurotransmitters. This balance changes as the amount of dopamine decreases. One way to restore this balance is with anticholinergic drugs. These drugs reduce the
amount of other neurotransmitters in the brain. They help maintain the correct balance of all neurotransmitters.
DRUGS WHOSE MODE OF ACTION IS UNCERTAIN. Sometimes drugs will work with PD patients, but researchers don't know why. The drug known as amantadine (pronounced uh-MANT-uh-deen, trade name Symmetrel) is an example. Amantadine is used to treat the symptoms of a variety of mental disorders. No one knows exactly how the drug relieves these symptoms, but it does, at least to a modest degree.
Some symptoms of Parkinson's disease occur because one part of the brain receives too much stimulation or another part receives too little. These problems can sometimes be helped by surgery. In one surgical procedure, a long thin needle is inserted into a certain part of the brain. The cells in that part of the brain are then killed with heat or electricity. This procedure prevents that region of the brain from becoming overactive.
A similar procedure can be used to make another part of the brain more active. A needle is inserted into the correct region of the brain. A mild electric current is then sent into the brain through the needle. The electric current may cause that region of the brain to become more active.
Surgery is used when patients do not respond to drugs or when drugs no longer work. Surgical procedures are often effective in helping people recover some of their normal muscular movement.
A third surgical procedure involves transplanting SN cells from the brain of a fetus. The brain cells in a fetus are in an early stage of development. When implanted into the brain of a PD patient, they sometimes take over the job of making dopamine. They begin to function in place of the patient's own SN cells that have lost the ability to produce dopamine. This procedure is still in an experimental stage.
Alternative treatments have limited promise for treating Parkinson's disease. Acupuncture, massage, and yoga may help relieve some symptoms of the disease by loosening tight muscles. Some alternative practitioners recommend the use of herbs and nutritional supplements, such as vitamins A, B, C, E, and the minerals calcium, selenium, and zinc. These supplements can sometimes have harmful side effects when used with drugs, however.