Parkinson's Disease - Are There Other Medications Available for Managing Disease Symptoms?
Levodopa is not a perfect drug. Fortunately, physicians have other treatment choices for particular symptoms or stages of the disease. Other therapies include the following:
- Bromocriptine and pergolide. These two drugs mimic the role of dopamine in the brain, causing the neurons to react as they would to dopamine. They can be given alone or with levodopa and may be used in the early stages of the disease or started later to lengthen the duration of response to levodopa in patients experiencing wearing off or on-off effects. They are generally less effective than levodopa in controlling rigidity and bradykinesia. Side effects may include paranoia, hallucinations, confusion, dyskinesias, nightmares, nausea, and vomiting.
- Selegiline. Also known as deprenyl, selegiline has become a commonly used drug for Parkinson's disease. Recent studies supported by the NINDS have shown that the drug delays the need for levodopa therapy by up to a year or more. When selegiline is given with levodopa, it appears to enhance and prolong the response to levodopa and thus may reduce wearing-off fluctuations. In studies with animals, selegiline has been shown to protect the dopamine-producing neurons from the toxic effects of MPTP. Selegiline inhibits the activity of the enzyme monoamine oxidase B (MAO-B), the enzyme that metabolizes dopamine in the brain, delaying the breakdown of naturally occurring dopamine and of dopamine formed from levodopa. Dopamine then accumulates in the surviving nerve cells. Some physicians, but not all, favor starting all parkinsonian patients on selegiline because of its possible protective effect. Selegiline is an easy drug to take, although side effects may include nausea, orthostatic hypotension, or insomnia (when taken late in the day). Also, toxic reactions have occurred in some patients who took selegiline with fluoxetine (an antidepressant) and meperidine (used as a sedative and an analgesic).
Research scientists are still trying to answer questions about selegiline use: How long does the drug remain effective? Does long-term use have any adverse effects? Evaluation of the long-term effects will help determine its value for all stages of the disease.
- Anticholinergics. These drugs were the main treatment for Parkinson's disease until the introduction of levodopa. Their benefit is limited, but they may help control tremor and rigidity. They are particularly helpful in reducing drug-induced parkinsonism. Anticholinergics appear to act by blocking the action of another brain chemical, acetylcholine, whose effects become more pronounced when dopamine levels drop. Only about half the patients who receive anticholinergics respond, usually for a brief period and with only a 30 percent improvement. Although not as effective as levodopa or bromocriptine, anticholinergics may have a therapeutic effect at any stage of the disease when taken with either of these drugs. Common side effects include dry mouth, constipation, urinary retention, hallucinations, memory loss, blurred vision, changes in mental activity, and confusion.
- Amantadine. An antiviral drug, amantadine, helps reduce symptoms of Parkinson's disease. It is often used alone in the early stages of the disease or with an anticholinergic drug or levodopa. After several months amantadine's effectiveness wears off in a third to a half of the patients taking it, although effectiveness may return after a brief withdrawal from the drug. Amantadine has several side effects, including mottled skin, edema, confusion, blurred vision, and depression.
