A drug long used in Germany slows the rate of memory loss and physical decline in advanced Alzheimer's patients, according to a study of what could be the first effective treatment for late stages of the mind-robbing ailment.

There is no cure or known prevention for Alzheimer's, which affects about 4 million Americans, and the only medications are approved for earlier stages of the disease.

But a six-month test of the drug memantine in patients with moderate-to-severe Alzheimer's showed it slowed deterioration from the disease, researchers report in Thursday's New England Journal of Medicine.

``It's a breath of fresh air for caregivers and for patients,'' said Dr. Barry Reisberg of New York University School of Medicine, who led the study.

A second study of memantine used with one of the current Alzheimer's drugs suggests the combination actually improves memory and thinking skills in advanced patients. That study is being presented Thursday at the American Academy of Neurology's annual meeting.

Memantine is not yet available in the United States, where government review is under way. It was approved for advanced Alzheimer's last year in Europe, where it has been available in Germany for two decades to treat dementia. Alzheimer's is a common form of dementia.

Reisberg's study was paid for by the German drug maker Merz Pharmaceuticals, whose employees were among the researchers. The second study was funded by Forest Laboratories Inc., which has U.S. marketing rights.

Memantine works differently than approved Alzheimer's drugs by blocking excess amounts of a brain chemical, glutamate, which can lead to nerve cell damage. The most commonly used Alzheimer's drugs _ Aricept, Exelon and Reminyl _ prevent the breakdown of another brain chemical.

Doctors usually keep Alzheimer's patients on those drugs as they move into later stages of the disease because they are thought to do some good, said Bill Thies, medical-science director of the Alzheimer's Association.

Memantine would give them a welcome option, he said.

``It does open the possibility that you can use the two together in a way that actually adds up to even greater benefit,'' Thies said.

In moderate to severe stages, Alzheimer's patients begin having trouble taking care of themselves and have problems with memory and thinking.

In the study by Reisberg's team, 252 patients were given either memantine or a dummy pill for six months and a battery of tests to measure their mental and physical abilities.

Both groups saw declines, but the group taking memantine declined by about half as much, Reisberg said. The findings also showed the burden on caregivers was reduced in the memantine group. Side effects were mostly mild, the researchers said.

In the combination study, the 403 patients were already taking one of the Alzheimer's drugs, Aricept. They were given either memantine or a dummy pill for six months.

The patients who got memantine showed a significant improvement in their memory and thinking, according to one of the researchers, Dr. Martin R. Farlow of Indiana University School of Medicine.

``The best of all worlds is if you can treat an illness with one medication but often the real world is you find drugs that work in different ways and you are able to gain additional benefits in patients,'' said Farlow. ``And I think that's what this study says.''

Harriette Bayse said there was a dramatic improvement in her former husband, William A. Bayse, after he began taking memantine in the combination study last year. She helps care for Bayse, 65, a retired FBI assistant director, who lives at a retirement community in Mount Pleasant, S.C.

``He was improving and improving, and by the summer... he was just really like his old self,'' she said.

She said he was talkative, could recall nicknames and his outlook was good. He continued taking memantine after the study, and the improvement lasted until recent seizures unrelated to the drug, she said.

``For my kids to be able to have the summer with him, Thanksgiving and Christmas, it was such a blessing,'' Bayse said.

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On the Net:

New England Journal: http://www.nejm.org

Alzheimer's Association: http://www.alzheimers.org