(HealthScoutNews) -- 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."