Parkinson's Disease - Medications

Compared to three of these agents, however, studies still report that L-dopa is superior for improving motor function, and, in one study, by year three was no difference in disease progression among all of the agents. Some studies suggest that, like L-dopa, they increase the risk for dyskinesia (uncontrolled movements).

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Side Effects. Side effects of pramipexole and ropinirole vary but can be severe and include the following:

Gastrointestinal side effects (nausea and constipation). Nausea can be controlled by drugs, such as domperidone.
Headache.
Orthostatic hypotension (sudden drop in blood pressure upon standing up).
Nasal congestion.
Nightmares, hallucinations, and even psychosis. (More severe than with L-dopa for both agents.)
Sudden sleep attacks. These can be very serious, particularly if patients are driving. (Sleep attacks may occur-although less commonly--with other PD drugs.)

Other Dopamine Agonists.

Specific dopamine agonists that contain ergot alkaloids include pergolide, bromocriptine (Parlodel), cabergoline, and lisuride. They are effective agents and some have been available for several decades. In general, they have a good safety record. Uncommon, but serious side effects have been reported with some of these agents, including scarring on the outside of the lungs or other organs and skin abnormalities. Experts recommend periodic monitoring for these side effects for patients taking any ergot-derived dopamine agonist.
Apomorphine is a dopamine agonist used as a single daily injection. It is particularly effective when administered as a "rescue" drug in people experiencing on-off effects severe enough to require going off L-dopa for a few days. Apomorphine may also be particularly helpful in alleviating nighttime symptoms, including pain and restless legs syndrome. It is rarely used, however, because it requires the addition of domperidone to control nausea. An injectable apomorphine (Apokyn) was approved by the FDA in 2004.

Catechol-O-Methyl Transferase (COMT) Inhibitors

Catechol-O-methyl transferase (COMT) inhibitors increase concentrations of existing dopamine in the brain. Entacapone (Comtan) is the current standard COMT inhibitor. It improves motor fluctuations related to the wearing-off effect and has shown good results in improving on time and reducing the requirements for L-dopa. If the patient does not respond to the drug within three weeks, it should be withdrawn. No one should withdraw abruptly from these drugs.

Side Effects. Side effects include the following:

Involuntary muscle movements.
Mental confusion and hallucinations.
Cramps, nausea, and vomiting.
Insomnia
Headache.
Urine discoloration. (This is a harmless side effect but should be reported.)
Diarrhea.
Less commonly, constipation, susceptibility to respiratory infection, sweating, dry mouth.