Parkinsons News:

Researchers Say Two Common Parkinson's Drugs Act Differently

Researchers at the Institute for Neurodegenerative Disorders in New Haven, CT, say a study of two of the drugs most frequently used to treat patients with Parkinson's disease may lead to ways to better treat the disease at an early stage.

The researchers said brain scans showed that the drugs, pramipexole and levodopa (L-dopa), which alleviate the motor symptoms of Parkinson's disease, act differently from each other.

Previous studies have shown that patients with early Parkinson's disease have lost 40 to 60 percent of dopamine neurons before their symptoms are diagnosed. Dopamine agonists are often the first choice of drug therapy for the initial treatment of the disease as they mimic the action of dopamine that has been lost by stimulating the dopamine receptors in the brain.

A double-blind randomized study compared the rates of dopamine neuron degeneration after initial treatment with pramipexole or levodopa in patients with early Parkinson's disease using single-photon emission computed tomography (SPECT), a scan that measures changes in brain chemistry. The brain scans were conducted on 82 patients over a four-year period.

Patients diagnosed with early Parkinson's disease who received initial treatment with pramipexole showed a slower decline of dopaminergic neuronal functioning compared with patients who received initial treatment with levodopa, the researchers reported in the Journal of the American Medical Association.

"While there remains debate about treatment for early Parkinson's disease -- and all treatment should be individualized to meet the needs of the patient -- this study adds important new information to the growing body of knowledge in the early treatment of Parkinson's disease," said Dr. Kenneth Marek, President of the Institute for Neurodegenerative Disorders.

Levodopa, the gold-standard treatment for Parkinson's disease, has been shown to lose its effectiveness over time. Long-term use of levodopa has also been linked with dyskinesias (involuntary jerking movements).

Prampiexole also has side effects including nausea, dizziness, drowsiness, insomnia, postural hypotension and hallucinations. There have also been reports of some patients falling asleep without warning signs of such as excessive drowsiness, even while driving a motor vehicle.

Investigators caution that more research is needed and the results do not mean that patients should change their medication.

Source: Medical Week staff, week of April 7, 2002