Even if the one relevant unpublished study was to find no effect of memantine on moderate to severe Alzheimer's dementia, the overall evidence from all studies would still tend in favor of the drug's use, the researchers concluded.
Two of the unpublished studies considered in the Cochrane review examine the drug's effect on mild cases of Alzheimer's dementia.
Although it appears that researchers finished collecting data for one of the studies in 2003, "the lack of any substantive reference to it suggests that the results may be less favorable than those in published studies," McShane says.
Dementia researchers caution that the drug does not protect brain cells from the disease.
"Memantine is a symptomatic treatment for Alzheimer's disease, not a cure for it," says Dr. Piero G. Antuono, a professor of neurology at the Medical College of Wisconsin. "It produces a delay in the progression of the disease for some time."
Memantine and other treatments for severe Alzheimer's disease "raise ethical issues," McShane says. "It is possible that the drug only extends the total time of deterioration without reducing the personal of social burden of the disease."
Alzheimer's disease is the most common cause of dementia. More than four million Americans have Alzheimer's, and the prevalence of the disease doubles every five years after age 65, according to the National Institute on Aging.
Vascular dementia is the second most common cause of dementia in western societies. In both types of dementia, there are no therapies proven to reverse the brain damage.
Becky Ham, Science Writer Health Behavior News Service
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Contact: Rupert McShane
rupert.mcshane@psych.ox.ac.uk
Center for the Advancement of Health
19-Apr-2005