According to new research, the drug donepezil, which has been used to treat mild to moderate Alzheimer's disease, is safe and effective when used to treat severe Alzheimer's as well.

The six-month study involved 343 people with severe Alzheimer's disease at clinics across the globe. Half of the group received a daily dose of donepezil; the other half received a placebo. Cognitive tests were performed throughout the study.

The study found cognitive function stabilized or improved in 63 percent of people taking donepezil, compared to 39 percent of people taking placebo. Those taking donepezil showed improvement in memory, language, attention and recognizing one's name. The donepezil group also showed less of a decline in social interaction, skills needed to complete a jigsaw puzzle and arranging sentences, compared to the placebo group.

"The effectiveness of donepezil in preserving cognitive and global function in people with severe Alzheimer's disease, as evidenced by this study and others, is encouraging," said study author Sandra Black, MD, Brill Professor of Neurology at Sunnybrook Health Sciences Centre, University of Toronto in Canada, and member of the American Academy of Neurology.

"People who progress to the severe stage of Alzheimer's disease have markedly diminished cognitive and global function, so preserving cognitive function is a worthwhile treatment goal because it may help to keep patients at home longer, something that patients and caregivers often desire and which delays the costs of nursing home care," said Black.

Black says the most common side effects reported in this study were mild to moderate. "Our findings provide further evidence that donepezil is safe, effective and benefits cognition and global function in people with severe Alzheimer's disease," she said.

The study was published in the July 31, 2007 issue of Neurology, the medical journal of the American Academy of Neurology.