Therapy for Parkinson's Disease Moving in the Right Direction
Oct. 17, 2000 -- How far have we come in finding the best treatment for Parkinson's disease? Recent research indicates that we're not quite there yet, but we are getting closer. Scientists are currently trying to determine whether a new class of drugs, developed in the last few years, can improve quality of life in these patients, and a recent study suggests they might.
More than 1 million Americans have been diagnosed with Parkinson's disease, which causes symptoms such as trembling even when the body is at rest, muscle rigidity, and loss of the ability to control voluntary movements. The disease is caused by the progressive death of nerve cells in the brain that produce a chemical called dopamine, which helps the central nervous system control normal movements.
Since the 1960s, standard therapy for Parkinson's disease has been the drug levodopa, which is marketed as Sinemet or Atamet. In the brain, levodopa is converted into dopamine to replace stores of the naturally occurring chemical.
But levodopa can be both a blessing and a curse. While the drug is effective at reversing motion problems, it also causes severe side effects in about 90% of all patients who use it long term. Side effects can include nausea, dizziness, hallucinations, and other abnormal, involuntary movements that often interfere with the patients' intended normal movements.
In addition, more and more of the drug is needed as the disease progresses, often making symptoms even worse. The symptoms can return suddenly and without warning, or they can wax and wane. It is a cruel irony, then, that the therapy itself often contributes to the ultimate disability associated with Parkinson's disease.
Mirapex (pramipexole) is one of a new category of drugs called dopamine agonists. Instead of being converted into dopamine in the brain, dopamine agonists boost the brain's ability to produce and process the chemical.
In a study published in the Oct. 18 issue of TheJournal of the American Medical Association, Mirapex reduced the risk of developing movement problems by as much as 55% in people who took it compared to patients who took levodopa. The research was conducted by investigators from the Parkinson Study Group.
As the Parkinson Study Group showed in a head-to-head comparison of pramipexole and levodopa, the newer drug can reduce or delay the onset of involuntary movements and the wearing off effects seen with levodopa therapy, says Robert Holloway, MD, MPH, medical director for the study and assistant professor of neurology at the University of Rochester (N.Y.), in an interview with WebMD.
The study showed, however, that levodopa provided better control of movement to patients than pramipexole, while causing fewer hallucinations, less sleepiness, and less swelling of tissues.
The findings echo those of a similar study comparing a different dopamine agonist called ropinirole to levodopa for treatment of early Parkinson's. In that study, published last May in The New England Journal of Medicine, Canadian and European researchers reported that "early Parkinson's disease can be managed successfully for up to five years with a reduced risk of [involuntary movements] by initiating treatment with ropinirole alone and supplementing with levodopa if necessary."