TUESDAY, Jan. 22, 2002 (HealthDayNews) -- Debunking previous research, a new study finds no connection between medications people with Parkinson's disease take and their sudden bouts of sleepiness while driving.
The finding is especially important in Canada, because that government has required warning letters about pramipexole (Mirapex) and ropinirole (Requip), based on studies suggesting they promote sleepiness, says Dr. Douglas E. Hobson, lead author and an assistant professor of neurology at the University of Manitoba.
"When the Canadian government requested the warning letters on these two drugs, it said the warning was pending further information," Hobson says. "This is further information."
The U.S. Food and Drug Administration has not issued a similar warning, but many doctors here have been cautious about prescribing the drugs.
Excessive daytime sleepiness is known to be common among patients with Parkinson's disease, in which a deficit of the brain chemical dopamine can cause trembling, stiffness, difficulty walking, and reduced mental function. The two drugs, which promote dopamine activity, have been reported to cause sudden sleepiness while driving.
But a study of 638 patients at 18 Canadian clinics found no such connection, says a report in tomorrow's issue of the Journal of the American Medical Association.
The researchers used the Epworth Sleepiness Scale and an Inappropriate Sleep Composite Score, specifically developed for the study, to determine not only the risk of falling asleep, but also how often it occurs.
They found 51 percent of the patients reported daytime sleepiness, and the number of times that happened was not affected by any medication the patients were taking. They also found the risk of the much-feared sudden onset of sleep while driving is rare. Only 16 patients reported a sudden onset of sleep while driving, and only 3 said it occurred without warning.
The score on the two tests, taken together, "is a useful tool to identify patients who are abnormally sleepy, and may play a role in increasing patient and physician awareness of this significant clinical problem," the journal report says.
"We were looking for predictors, because everyone was told they shouldn't drive," Hobson says. "This will be helpful in selecting out the patients who shouldn't be driving."
The study is also useful because it gives solid information about unwanted sleepiness, he says.
"No one knew how often it happens," Hobson says. "Knowing the frequency will help a lot in relation to regulations about driving."
The study will help doctors treating Parkinson patients because it gives them a way of identifying patients at high risk of unwanted sleepiness, says Dr. Cynthia L. Comella, of Rush-Presbyterian-St Luke's Medical Center in Chicago.
"The most important point of the study is the ability to measure
sleepiness in Parkinson's disease," says Comella, who wrote an accompanying editorial. "The method is quite simple
and clinically applicable. Until now, nothing has been shown to assess
sleepiness in correlation with driving."
What To Do
"Patients considered to be at risk for falling asleep behind the wheel should be cautioned to avoid driving, regardless of the drug treatment," Comella writes.
Basic information about Parkinson's disease can be found at the National Institute of Neurological Disorders and Stroke or the National Parkinson Foundation.
