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Mirapex (Pramipexole) May Slow Loss of Dopamine Cells in Parkinson's Disease Patients: Presented at AAN

By Ed Susman

Special to DG News

DENVER, CO -- April 17, 2002 -- Initial treatment with the dopamine agonist Mirapex (pramipexole) appears to slow the progressive loss of dopamine cells in patients with Parkinson's disease more effectively than does levodopa.

"This is the first example in which we have evaluated the progression of Parkinson's Disease which shows there is a difference in brain activity as a result of a treatment," said Dr. Kenneth Marek, MD, president of the Institute for Neurodegenerative Disorders, New Haven, Connecticut, speaking at the 54^th annual meeting of the American Academy of Neurology (AAN).

To determine whether initial treatment with either levodopa or the dopamine agonist pramipexole influenced progression of Parkinson's disease, the researchers selected 82 patients from the Comparison of the Agonist Pramipexole vs. Levodopa on Motor complications in Parkinson's Disease (CALM-PD) study. To track the loss of dopamine cells in patients with Parkinson's disease, Dr. Marek and colleagues used [¹²³I]ß-CIT SPECT imaging.

He said the trial, sponsored by Pharmacia Corporation and Boehringer Ingelheim, demonstrated that patients who started therapy on the pramipexole had less of a reduction in dopamine than those patients who began therapy on levodopa.

Results showed a decline in [¹²³I]ß-CIT striatal uptake in the study cohort of 10.3±9.8 percent at 22 months, 15.3±12.8 percent at 34 months and 20.7±14.4 percent at 46 months. The decline was approximately a rate of 5.2 percent per year overall throughout the evaluation period.

A comparison of the two treatment arms showed a significantly reduced loss in striatal [¹²³I]ß-CIT uptake from baseline in the pramipexole arm compared to the levodopa arm, as follows: 7.1±9.0 percent vs. 13.5±9.6 percent at 22 months p=0.004; 10.9±11.8 percent vs. 19.6±12.4 percent at 34 months, p=0.009; and 16.0±13.3 percent vs. 25.5±14.1 percent at 46 months, p=0.01.

The percent loss in striatal [¹²³I]ß-CIT uptake from baseline was correlated with the change from baseline in Unified Parkinson Disease Rating Scale at the 46 month evaluation, r=0.40, p=0.001.

"Patients treated initially with pramipexole demonstrated a relative reduction in the rate of loss of striatal [¹²³I]ß-CIT uptake of approximately 40 percent compared to those treated initially with levodopa during a 46-month evaluation period," Dr. Marek said. "These imaging data strongly suggest that treatment with pramipexole may slow and/or levodopa may accelerate the rate of loss of nigrostriatal dopamine neurons in early Parkinson's disease patients."

Dr. Marek said the results suggest that patients with Parkinson's disease will do better if their initial treatment is in the form of a dopamine agonist such as pramipexole.

The findings were even more impressive when looked at with the results of a trial with ropinirole, another dopamine agonist, which achieved similar outcomes. In the ropinirole study, dopamine levels declined by 20 percent with levodopa, and by 13 percent with ropinirole-a relative risk reduction of about 35 percent over the two-year study. Taken together, he said, the findings indicate that dopamine agonists should be front-line treatment for most patients who are newly diagnosed with Parkinson's disease.

"Most neurologist already prescribe dopamine agonists first," said Abraham Lieberman, MD, professor of neurology at the University of Miami, in Miami, Florida, and medical director of the National Parkinson's Foundation. "However, it appears that this message hasn't yet reached internists and family practitioners who treat about half the Parkinson's patients in the United States."

Ray Watts, MD, professor of neurology at Emory University, in Atlanta, Georgia, one of the ropinirole investigators, suggested that the dopamine agonist treatment should be first line among younger patients. Elderly individuals with comorbidities might do well on levodopa, since there could be a heightened risk of undesirable side effects in older people with the dopamine agonists.

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