Side Effects of Medication

Thanks to drug treatment, people with Parkinson's disease can lead normal, productive lives for many years. However, like all drugs, Parkinson's medications are not without side effects. Some are obvious and occur soon after you start taking the drug, but others may be more subtle and appear only after you’ve been on a medication a while.

Among the most widely used Parkinson’s medications, there are specific side effects you should be aware of after you or your loved one has been taking them for a few months or more.

Parkinson's Disease Treatment Side Effects: Dopamine Agonists

Parkinson’s disease is caused by a deterioration of nerve cells in certain parts of the brain that produce a neurotransmitter called dopamine. Parkinson's medications known as dopamine agonists control many of the symptoms of Parkinson’s disease by mimicking the actions that dopamine is responsible for. Usually, this medication is prescribed in the early stages of the disease. Drugs in this category include:

·         Mirapex (pramipexole)

·         Requip (ropinirole)

·         Parlodel (bromocriptine)

·         Permax (pergolide) — no longer available in the United States.

The short-term side effects of this type of Parkinson's medication may include nausea, sleep disturbances such as insomnia or vivid dreams, low blood pressure, and chest or abdominal pain. But perhaps the most troubling side effect associated with dopamine agonists is the potential for high-risk behaviors, such as compulsive gambling or having indiscriminate sex.

In one recent study, doctors at the Mayo Clinic reviewed the medical records of 267 people with Parkinson’s disease. Of the 66 people who were taking a dopamine agonist, seven — more than 10 percent — had started engaging in compulsive gambling or excessive sexual activity after they began taking the Parkinson's medication. Of those experiencing this side effect, the behavior was clearly pathological and disabling for at least five. In some cases, the abnormal behavior appeared within just two or three months after the patient started taking the Parkinson's medication, although for other people, it took up to a year or two for the changes in behavior to show up. Parkinson's patients who were not taking dopamine agonists did not develop these problems.

Discontinuing the dopamine agonist or lowering its dose seems to end the harmful behavior in those who experience this side effect. If you or someone you love is taking one of these drugs, watch for any increase in risky behavior and if you note any such behavior, tell his or her doctor right away so that changes can be made.

Parkinson's Disease Treatment: Carbidopa/Levodopa

Sold under the brand name Sinemet, Atamet, or Parcopa, the combination of carbidopa/levodopa is considered the “gold standard” of drug treatment for Parkinson’s disease and has improved life for millions of people with Parkinson's disease. Unfortunately, however, it’s not problem-free. After several years of taking this drug combo, some people develop abnormal, involuntary writhing movements called dyskinesias. Many people are willing to live with mild dyskinesias as long as their Parkinson’s symptoms are under control. However, more serious dyskinesias may be modified by taking smaller overall doses of carbidopa/levodopa or by taking smaller doses at shorter intervals, keeping the overall dose the same.

Also, while carbidopa/levodopa and other Parkinson’s disease medications can control symptoms for a while, they do not keep the disease from progressing. As time goes on and the illness becomes more severe, your response to carbidopa/levodopa may start to fluctuate, leading to what doctors call “on-off” periods. As your “on” response times grow shorter, you may find it harder to walk, eat, bathe, or speak, even if it’s not yet time for the next dose of your medication.

When this happens, your doctor may change your drug dose or schedule, or may prescribe a medication called Stalevo, that combines carbidopa/levodopa with a drug called entacapone, prolonging the action of levodopa in the brain by as much as 10 percent and resulting in longer “on” periods.

Diet may also make a difference. Protein can interfere with the absorption of levodopa from the digestive tract into the bloodstream. Some people find that taking their medication at least 30 minutes before or 60 minutes after a meal enhances their response to the drug.

Parkinson's Disease Treatment: COMT Inhibitors

Comtan (entacapone) and Tasmar (tolcapone) belong to a category of agents called COMT inhibitors. They’ve been associated with diarrhea after a few months of use. Tasmar is prescribed much less frequently than Comtan because it has been linked to liver failure in some people. If you take Tasmar, your doctor will most likely want to perform blood work every few months to monitor your liver function.

Good communication with your doctor is the key to preventing or minimizing most of these side effects from Parkinson's medication: Alert your doctor as soon as anything unusual occurs. Often the problem can be solved by changing the medication dose or schedule, or by substituting another drug. In general, it’s a good idea to keep track of all the drugs you’re taking and review them with your doctor at every visit.

Last Updated: 06/10/2009