But the Food and Drug Administration's advisers struggled with how much benefit memantine actually offers, and if it could give false hope to families of the most severely ill patients.
"I believe this to be a very small effect size," cautioned the panel's chairwoman, Dr. Claudia Kawas of the University of California, Irvine. "The entire committee has certain concerns."
When it comes to benefit for the most severe Alzheimer's patients, "I'm very unimpressed," added Dr. Roger Packer, a neuroscientists in Washington.
Still, the FDA panel voted unanimously that memantine does offer some benefit to people with moderate to severe Alzheimer's symptoms, and is safe enough to try.
If the FDA ultimately agrees, memantine would mark an important step in Alzheimer's therapy. The nation's four other Alzheimer's medications are designated for early stages of the disease, and they work on a different brain chemical than memantine. The new drug could let doctors, for the first time, prescribe drug combinations in hopes of better results.
The FDA is not bound by its advisers' recommendations but typically follows them. A decision could come as early as this fall.
Families out of options are anxiously awaiting memantine; many now try to buy supplies overseas via the Internet. The drug's U.S. marketer, Forest Laboratories, says it receives over 1,000 calls a month from families desperate to buy it in this country.
"These are priceless moments regained," said Barry Cooper of Arlington, Va., who told the FDA panel that his wife, Linda, talks more and regained some small skills since starting memantine bought abroad.
"Every month can count," he added, urging that FDA act quickly.
Memantine is not miraculous, even company-affiliated researchers acknowledged. But it can help stabilize patients so that they maintain certain functions for a few months longer, said Dr. Pierre Tariot of the University of Rochester, who led one of the critical studies.
He said studies suggest memantine gives some patients the ability go to the toilet independently for six more months, "and that's very important."
It is not known if memantine might help in earlier stages of Alzheimer's. Studies of that question are in progress.
Forest has not announced a projected U.S. price. One Internet site advertises the drug for about $146 for a month's supply.
About 4 million Americans have Alzheimer's, and a million of them are believed to suffer severe symptoms. There is no known cure or prevention.
A six-month study of patients with moderate to severe Alzheimer's symptoms found those given memantine worsened significantly slower — by one measure, at half the pace, according to researchers. In a second study, patients taking the older Alzheimer's drug Aricept found added benefit when they took memantine, too.
Some patients reported actual improvements in memory and thinking skills. For the majority, however, the drug simply slowed the pace of deterioration.
FDA panelists could not say how much benefit patients got. More confusing, when FDA's scientists looked at just the most severely ill patients, in one study memantine seemed to have no effect and only moderately ill patients were helped.
FDA's advisers could not say how the average doctor would know who should get the pill and when the medication would be a waste of time.
Today's Alzheimer's drugs — Aricept, Exelon, Reminyl and Cognex delay the breakdown of a brain chemical called acetylcholine that is vital for nerve cells to communicate. Memantine blocks excess amounts of another brain chemical, called glutamate, that can damage or kill nerve cells.
Memantine has been sold in Germany for two decades to treat various brain diseases, with few, mild side effects reported to date. In 1999, the first large studies suggesting memantine helped advanced Alzheimer's were published, prompting U.S. research.
German drug-maker Merz Pharmaceuticals last year won Europe-wide approval of memantine for advanced Alzheimer's, and Forest Laboratories filed for FDA approval in late December.