Memantine should be on pharmacy shelves by January under the brand name Namenda, its marketer says. The drug has been sold for two decades in Germany, desperately sought by many U.S. families since word of its promise began spreading last year.

It was approved Friday by the Food and Drug Administration.

The marketer, Forest Laboratories Inc., says it has been getting over 1,000 calls a month from people waiting to buy it. Others have been buying supplies overseas via the Internet.

Memantine does not offer miraculous benefits, said the FDA, worried about giving families false hope.

The drug can delay worsening from Alzheimer's, however, allowing people to maintain functions such as going to the bathroom independently for a few months longer.

It's the first option specifically for people with moderate to severe Alzheimer's symptoms. Today's other four Alzheimer's medications are proved to work only in early stages of the disease.

Perhaps more importantly, memantine works on a different brain chemical than the other four drugs. That means for the first time, doctors can combine different Alzheimer's therapies in hopes of better results.

Today, some families import memantine from Europe for prices ranging from $147 to $240 for a month's supply. Forest Laboratories, which licensed the drug from German maker Merz Pharmaceuticals, refused to say whether U.S. prices would fall within that range, saying it had not yet decided.

Ruth Hobbs, 74, of Winchester, Ky., has been taking a combination of memantine and the older Alzheimer's drug, Aricept, for about a year in a research project.

A year ago, Hobbs couldn't remember Thanksgiving had even occurred. This year, she's planning to help cook, and her family credits the combination with allowing her to continue living alone.

"We had reached a point where we were saying, `What are we going to do about Mama?'" recalled DeEtta Blackwell, Hobbs' daughter. Now, "we're not waiting for the other shoe to drop."

About 4.5 million Americans have Alzheimer's, and a million of them are believed to suffer severe symptoms. It afflicts mainly the elderly, robbing them of memory and the ability to care for themselves. There is no known cure or prevention; medications only temporarily slow the inevitable worsening.

Memantine has been used in Germany for two decades to treat different brain disorders. In 1999, the first solid research was published that suggested memantine could help moderate to severe Alzheimer's; the drug won Europewide approval for that use last year.

In U.S. studies, some patients experienced improvements in memory and other skills, like Hobbs.

But for most, the drug instead slowed the pace of deterioration, by some measures at half the pace of those given a dummy drug. Performance was measured on cognitive tests and by tracking how well patients performed certain functions such as getting dressed or bathing themselves.

"The effect wasn't overwhelming," cautioned FDA neurologic drugs chief Dr. Russell Katz. "But they did better than they would have done if they hadn't gotten anything."

And for families facing the prospect of round-the-clock care, maintaining even some simple activities for an extra six months is very important, said Zaven Khachaturian, senior science adviser of the Alzheimer's Association.

"Having another one, that operates on a different principle, is welcome news," he said.

The four other Alzheimer's medications -- Aricept, Exelon, Reminyl and Cognex -- work by delaying the breakdown of a brain chemical called acetylcholine, which is vital for nerve cells to communicate. In contrast, memantine blocks excess amounts of another brain chemical, called glutamate, that can damage or kill nerve cells.

Doctors don't yet know whether memantine works better when given in early stages of Alzheimer's; those studies are under way.

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