Parkinson's Disease - Surgery

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Dopamine Agonists

Dopamine agonists stimulate dopamine receptors in the substantia nigra, the part of the brain in which Parkinson's is thought to originate. Dopamine agonists are effective in delaying motor complications during the first 1 or 2 years of treatment.

Newer Dopamine Agonists. The most commonly prescribed dopamine agonists are pramipexole (Mirapex) and ropinirole (Requip). They are used either alone or in combination with L-dopa. Pramipexole appears to work better and have fewer side effects than ropinirole.

Recent research suggests that L-dopa is better at improving motor disability, and dopamine agonists are better at reducing motor complications. L-dopa has a higher risk for dyskinesia side effects than dopamine agonists, but dyskinesia (difficulty controlling muscle movements) can also occur with dopamine agonists. There is debate about the value of dopamine agonists as initial therapy for Parkinson’s disease. Recent research suggests that early treatment with dopamine agonists may not provide any long-term advantages compared with starting treatment with L-dopa.

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

• 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 psychosis (more severe than with L-dopa for both drugs)
• Sudden sleep attacks. These can be very serious, particularly if patients are driving.

Other Dopamine Agonists.

• Specific dopamine agonists that contain ergot alkaloids include bromocriptine (Parodel), pergolide (Permax) and lisuride (Dopergin). Bromocriptine is the only ergot dopamine agonist approved for Parkinson's treatment in the United States.
• Apomorphine is a dopamine agonist used as a "rescue" drug in people having on-off effects severe enough to require going off L-dopa for a few days. It is FDA-approved for treating off-time episodes of Parkinson's disease. Apomorphine is given by injection. Because it causes severe nausea and vomiting, it must be taken with an anti-nausea drug.