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U.S. study finds Parkinson's drug presents trade-offs
CHICAGO, Illinois (Reuters) -- A drug that calms the tremors of Parkinson's disease by acting on the body's use of a key brain chemical produced favorable results in a two-year trial, though it caused side effects that included hallucinations, a study said on Tuesday.
In a report on the trial published in this week's Journal of the American Medical Association, 151 early-stage Parkinson's sufferers given the drug pramipexole saw a significant reduction in one of the complications from the progressive disease.
The standard treatment for Parkinson's has been levodopa, which the body converts into the neurotransmitter dopamine, the chemical messenger that controls muscle movement and gradually diminishes in victims.
Levodopa eases the shaking, muscle rigidity, speech and swallowing difficulties symptomatic of the disease caused by the unexplained die-off of dopamine-producing brain cells.
But levodopa patients also develop involuntary, spasmodic hand, arm and leg movements, called dyskinesia, which can become disabling. The drug also gradually loses its effectiveness.
In the ongoing U.S. study, funded primarily by pramipexole's manufacturer, Pharmacia Corp., the patients taking the drug developed one-third fewer of the dyskinesias than levodopa patients.
But pramipexole, a newer member of a class of drugs called dopamine agonists that act on the body's cell receptors for dopamine, was not as effective as levodopa at controlling the disease's early-stage symptoms.
The drug also produced side effects in some patients that included hallucinations, sleepiness and an abnormal buildup of fluid in body tissues called edema.
Existing dopamine agonists are used in conjunction with levodopa to smooth out the highs and lows of motor control that many patients experience.
"There's a trade-off here that physicians and patients have to be aware of when deciding what therapy to begin," said study author Robert Holloway, a neurologist at the University of Rochester in New York.
"Pramipexole clearly reduces the occurrence of developing abnormal motor movements, but levodopa is associated with better symptom control and less chance of sleepiness and hallucinations. It's a balance of adequately controlling the disease and the complications that often result from treatment," Holloway said.
Roughly one million people in the United States -- including Attorney General Janet Reno and actor Michael J. Fox -- are thought to suffer from Parkinson's. The world market for drugs to treat the disease was estimated at $1.6 billion last year.
"For 30 years the initial treatment of this disease has been straightforward. Now, there is a real choice that doctors and patients should be discussing," said the University of Rochester's Ira Shoulson, who heads the Parkinson's Study Group that conducted the trial.
"As the proportion of the U.S. population at risk for Parkinson's disease increases, a long-term approach to therapy assumes increasing importance," Caroline Tanner of the Parkinson's Institute in Sunnyvale, California, wrote in an accompanying editorial published in the AMA journal.
Other potential therapies for advanced Parkinson's cases such as stem cell transplants, gene therapy and surgery need to be explored and evaluated, she wrote.
"Understanding the relationship between the initial treatment of Parkinson's disease and outcomes such as morbidity, mortality and responsiveness to therapies for advanced disease will be needed. Other outcomes, such as the cost and effectiveness of a particular therapy, are virtually unexplored," Tanner said.
Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
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