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Study Suggests L-Dopa May Slow PD Progression

Since the day it burst onto the scene as a miracle drug in the early 1970s, L-Dopa has been hailed as the “gold standard” of therapy to ease the symptoms of Parkinson’s disease. Over all these years, a recurring question in scientific circles has been whether the medication may actually play a role in slowing or accelerating the course of the disease itself.

Now, thanks to a study organized and executed by the leading nationwide consortium of Parkinson’s research centers, the Parkinson Study Group, and financially supported by NIH and the Department of Defense, we have the beginnings of an answer to this question. Simply put: there is no evidence, from clinical examination of patients’ PD symptoms and various “quality of life” measures, that Sinemet (a compound of L-Dopa with the supporting ingredient carbidopa) harms patients or exacerbates Parkinson’s. Indeed, there is some evidence that it may actually be “neuroprotective” — that is, it may protect the remaining healthy brain cells and thereby help to slow the course of the disease.

However, when the same patients were studied using a sophisticated new brain-imaging technique known as a Beta-CIT scan, the report card on L-Dopa was less encouraging. Images taken at the end of the nine-month term of the trial showed evidence that the patients taking Sinemet had a greater reduction of beta-CIT binding than those in the “control group” who were not taking the drug. There is uncertainty about whether this reduction of binding means more loss of dopamine neurons or whether it represents some pharmacological properties of L-Dopa.

These and other findings of the study were announced in Miami in mid-November at the biennial International Congress of the Movement Disorders Society, a worldwide group of experts on Parkinson’s disease and other movement disorders. The principal investigator, who was also the presenter at the Miami conference, was Dr. Stanley Fahn, H. Houston Merritt professor of neurology at Columbia Presbyterian Medical Center in New York City. Dr. Fahn also serves as Scientific Director of PDF and is the current Chair of the American Academy of Neurology.

“Patients should, in general, be encouraged by these results, tentative though they may be,” Dr. Fahn said in an interview following his presentation. “There is no evidence from the clinical data that any harm will come to them by taking Sinemet and indeed some reason for hope that the medication may slow the progression of the disease.” He warned, however, that “we need to do further studies to resolve the apparent incongruity between the clinical and imaging evidence.”

Clinical Measures Suggest an Extended Benefit From Sinemet Use

The study took 360 patients at 10 research centers and divided them into four groups. One was a “control” group (that is, they were given dummy or “placebo” pills resembling Sinemet) and the other three were given different doses of Sinemet, from 150 mg per day to 600 mg. All groups were kept on their respective regimens for 40 weeks, following which their systems were “washed out” for a period of two weeks to remove evidence of the drug. At this point, symptoms were measured again and the results compared with the original baseline (that is, their condition at the outset of the study).

The results, measured according to the widely-used scale of symptoms known as the Universal Parkinson’s Disease Rating Scale, showed that all three of the L-Dopa-taking groups did much better overall and in each of the three major categories: mental function, motor function and ability in the activities of daily living than the placebo group (which showed a significant worsening of condition). Two of the L-Dopa-taking groups were only slightly worse off than they had been at baseline and the third – the one with the highest dose of L-Dopa – actually showed a slight improvement in condition over baseline.

Teva Pharmaceuticals of Netyana, Israel, generously provided the medications and placebos used in this study.

Source Date: Jan 01 2003