Levodopa

BRAND: Dopar, Larodopa

The gold standard of present therapy is the drug levodopa (also called L-dopa). L-Dopa (from the full name L-3,4-dihydroxyphenylalanine) is a neutral amino acid found naturally in plants and animals. After oral ingestion, it is absorbed in the small intestine. Absorption can be delayed by meals and increased gastric acidity. Absorbed levodopa is not bound to plasma protein. Nerve cells can use levodopa to make dopamine and replenish the brain's dwindling supply. Dopamine cannot be given directly because it doesn't cross the blood-brain barrier, the elaborate meshwork of fine blood vessels and cells that filters blood reaching the brain. Levodopa crosses the blood-brain barrier by way of the large neutral amino acid carrier transport system.

Levodopa is used to treat the stiffness, tremors, spasms, and poor muscle control of Parkinson's disease. Levodopa is also used to treat these same muscular conditions when they are caused by drugs such as chlorpromazine (Thorazine), fluphenazine (Prolixin), perphenazine (Trilafon), and others.

Usually levodopa is given combined with carbidopa. When added to levodopa, carbidopa delays the conversion of levodopa into dopamine until it reaches the brain, preventing or diminishing some of the side effects that often accompany levodopa therapy. Carbidopa also reduces the amount of levodopa needed by about 75%.

Levodopa delays the onset of debilitating symptoms and allows the majority of parkinsonian patients to extend the period of time in which they can lead relatively normal, productive lives.

Levodopa helps about 75% of parkinsonian cases. It cannot treat all symptoms associated with Parkinson's disease. Bradykinesia and rigidity respond best, while tremor may be only marginally reduced. Problems with balance and other symptoms may not be alleviated at all.

Once levodopa therapy starts people often respond dramatically, but they may need to increase the dose gradually for maximum benefit.

Since a high-protein diet can interfere with the absorption of levodopa, protein consumption may have to be limited to your evening meal when taking this medicine.

Levodopa is so effective that some people may forget they have Parkinson's disease. But levodopa is not a cure. Although it can diminish the symptoms, it does not replace lost nerve cells and is does not stop the progression of the disease.

Important Information About Levodopa

Call your doctor immediately if you experience uncontrollable movements of your face, eyelids, mouth, tongue, neck, arms, hands, or legs; severe or persistent nausea or vomiting; an irregular heartbeat or fluttering in your chest; or unusual changes in mood or behavior.

Use caution when driving, operating machinery, or performing other hazardous activities. levodopa may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities.

Avoid vitamin products that contain vitamin B6 (pyridoxine). This vitamin will reduce the effectiveness of levodopa.

Side Effects of Levodopa

The most common side effects of Levodopa are:

Confusion may improve with a decrease in levodopa dose. Hallucinations and delusions can be treated with clozapine.

People who take large doses of levodopa over an extended period are susceptible to dyskinesias (involuntary movements such as twitching, nodding, and jerking). These movements may be mild or severe and either very rapid or very slow. The only effective way to control these drug-induced movements is to lower the dose of levodopa or to use drugs that block dopamine, but these remedies usually cause the disease symptoms to reappear.

Patients, who take Levedopa for an extended period of time, may begin to notice more pronounced symptoms before their first dose of medication in the morning, and they can feel when each dose begins to wear off (muscle spasms are a common effect). Symptoms gradually begin to return. The period of effectiveness from each dose may begin to shorten, called the wearing-off effect.

Another potential problem is referred to as the on-off effect- sudden, unpredictable changes in movement, from normal to parkinsonian movement and back again, possibly occurring several times during the day. These effects probably indicate that the patient's response to the drug is changing or that the disease is progressing.

One approach to alleviating these side effects is to take levodopa more often and in smaller amounts. Sometimes, physicians instruct patients to stop levodopa for several days in an effort to improve the response to the drug and to manage the complications of long-term levodopa therapy. This controversial technique is known as a "drug holiday." Because of the possibility of serious complications, drug holidays should be attempted only under a physician's direct supervision, preferably in a hospital. Parkinson's disease patients should never stop taking levodopa without their physician's knowledge or consent because of the potentially serious side effects of rapidly withdrawing the drug.

Who should not take levodopa?

Do not take levodopa if you have taken a monoamine oxidase inhibitor (MAOI), such as isocarboxazid (Marplan), tranylcypromine (Parnate), or phenelzine (Nardil), which are used to treat depression, in the past 2 weeks.

It is not known whether levodopa will harm an unborn baby. Do not take levodopa without first talking to your doctor if you are pregnant.

It is also not known whether levodopa will harm a nursing infant. Do not take levodopa without first talking to your doctor if you are breast-feeding a baby.

If You overdose - Seek emergency medical attention.

Symptoms of a levodopa overdose include nausea, diarrhea, vomiting, weakness, fainting, confusion, hallucinations, muscle twitching, and agitation.

Next Topic: Carbidopa and Levodopa

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