Riluzole to Treat Parkinson's Disease

This study will evaluate the effects of the drug riluzole on Parkinson's disease symptoms and on dyskinesias (involuntary movements) that develop as a result of long-term treatment with levodopa. Riluzole blocks the action of the chemical messenger glutamate, thought to be involved in producing Parkinson's symptoms. The drug is currently approved to treat amyotrophic lateral sclerosis, another neurologic condition.

Patients with relatively advanced Parkinson's disease between 20 and 80 years of age may be eligible for this 4-week study. Participants will have a complete medical history and physical examination, and a detailed neurological evaluation. The evaluations will include blood tests and an electrocardiogram, and possibly brain magnetic resonance imaging (MRI), CT scan, and chest X-ray.

Participants will, if possible, stop taking all antiparkinsonian medications except levodopa (Sinemet) for one month before the study begins and throughout its duration. For the first 1 to 3 days, patients will be admitted to the NIH Clinical Center to undergo a levodopa "dose-finding" procedure. For this study, patients will stop taking their oral Sinemet and instead will have levodopa infused through a vein for up to 8 hours/day. During the infusions, the levodopa dose will be increased slowly until either 1) parkinsonian symptoms improve, 2) unacceptable side effects occur, or 3) the maximum study dose is reached. Symptoms will be monitored frequently to find two infusion rates: 1) one that is less than what is needed to relieve symptoms (suboptimal rate), and 2) one that relieves symptoms but may produce dyskinesias (optimal rate).

When the dose-finding phase is completed, treatment will begin. Patients will take riluzole or placebo (a look-a-like pill with no active ingredient) twice a day, along with their regular Sinemet, for 3 weeks. (All participants will receive placebo at some time during the study, and some patients will receive only placebo throughout the entire 4 weeks.) At the end of each week, patients will be readmitted to the hospital and receive the previous week's dose of riluzole or placebo in combination with a levodopa infusion at the rate determined in the dose-finding phase of the study. The procedure for the infusion will be the same as that for the dose-finding phase. The dose of riluzole will be increased until the optimum dose has been achieved or until side effects occur (at which time the dose will be lowered or the drug stopped).

Throughout the study, parkinsonian symptoms and dyskinesias will be evaluated using standardized rating scales and blood samples will be drawn periodically to measure drug levels.