Clinical trial established that two drugs, levodopa and pramipexole, are both viable initial treatments for Parkinson's disease

McGill University researchers took part in a major North American study to compare two treatments for Parkinson's disease.

The four-year clinical trial established that two drugs, levodopa and pramipexole, are both viable initial treatments for Parkinson's disease, a degenerative disorder of the central nervous system.

Findings on pramipexole versus levodopa were produced by the Parkinson's Study Group (PSG) and are reported in the Archives of Neurology. Some 301 participants were evaluated at 22 PSG sites in the United States and Canada. The PSG is a non-profit cooperative of Parkinson's disease experts from the U.S. and Canada who are dedicated to improving treatment for Parkinson's disease. (Information)

Michel Panisset, director of the Movement Disorders Clinic at the McGill Centre for Studies in Aging, along with nurse coordinator Jean Hall, followed 13 of the Canadian participants. The primary goal of the study was to monitor treatment complications: wearing off (feeling that the drug effect lessens before the next dose) and dyskinesias (involuntary movements).

The PSG compared levodopa, the most commonly used drug to treat the early symptoms of Parkinson's, to pramipexole, a newer dopamine agonist that works as artificial dopamine. Patients with early Parkinson's who were treated with pramipexole reported a reduction of involuntary movements and wearing off of the drug, compared to treatment with levodopa.

Yet researchers found treatment with levodopa resulted in a lower incidence of somnolence, swelling in the feet and legs (edema), and better motor performance. These findings were measured by the Unified Parkinson's Disease Rating Scale (UPDRS), a monitoring system used extensively by researchers and clinicians around the world since its 1987 introduction. (Information)

After four years, researchers found that 52 percent of subjects assigned to initial pramipexole treatment experienced a first occurrence of motor complications, or "wearing off" of the drug's effect, compared with 74 percent of the levodopa-initiated subjects. Researchers found average improvement in total UPDRS scores, measured at the first and last study visit, was greater in the levodopa group than in the pramipexole group. The most commonly observed side effects of pramipexole were somnolence and edema, while side effects of levodopa included abnormal neuromuscular conditions, dyskinesias and wearing off.

The study was supported by Boehringer/Ingelheim Pharmaceuticals, Inc. and Pfizer Inc., who co-promote MIRAPEX (pramipexole) in the United States for Parkinson's disease.