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THURSDAY, June 24 (HealthDayNews) -- Cholinesterase inhibitors, the most widely prescribed drugs for Alzheimer's disease, do not slow progression of the mind-robbing condition and do not affect the rate at which patients must be admitted to nursing homes, a British study finds.

The drugs, which include donepezil (Aricept), galantamine (Reminyl) and rivastigmine (Exelon), do provide some benefits, but not nearly enough to justify their widespread use, said Richard Gray, professor of medical statistics at the University of Birmingham and lead author of a report on the study in the June 26 issue of The Lancet.

The results of the study also contradict claims made by pharmaceutical companies who market the drugs on the basis of studies they have financed, he said. But the makers of the leading drug, Aricept, defended their research.

Alzheimer's drug trials financed by drug companies are often "very seriously flawed," Gray said, because they are short in duration -- usually only about six months -- and are made up of Alzheimer's patients who independently choose to take the drugs. These types of patients tend to have more benign, slowly progressing disease, so it's tough to measure whether the drugs would provide significant relief for more serious symptoms over the long term.

By contrast, the new study is a placebo-controlled, randomized, double-blind trial in which 486 participants were chosen at random from persons diagnosed with Alzheimer's disease. Neither doctors nor patients knew who was taking the active drug or an inactive sugar pill, and the patients were followed for several years.

The drug used in the trial, Pfizer, Inc.'s donepezil (Aricept), is the most widely prescribed medication of its class, but the study results should hold true for other cholinesterase inhibitors, Gray said.

Those results were not encouraging.

After an average of three years, 42 percent of those taking Aricept were hospitalized, compared to 44 percent taking the placebo, a difference that was not statistically significant. Progression of disease-related disability occurred in 58 percent of those taking Aricept and 59 percent of those taking placebo. No differences were found in symptoms, cost of care, adverse medical events, or death rates.

Aricept did improve performance on tests of mental and functional ability, but Gray dismisses them as unimportant. "They usually ask such questions as spell the word 'world' backwards," he said. "Is it worth spending £1,000 a year [about $1,800] to be able to spell the word 'world' backwards?"

A statement by Pfizer, which markets the drug in the United States, and Eisai, Inc., which markets it in England, challenged the results of the study. They "have limited value when compared to the extensive data gathered for cholinesterase inhibitors in tens of thousands of patients derived from carefully monitored and validated studies," the statement reads.

An "overwhelming body of evidence and real-world experience" supports the use of Aricept and similar drugs for Alzheimer's patients, and "doctors, in consultation with the patients and caregivers, should continue treating patients with Alzheimer's disease based on their clinical experience and expertise," the statement continued.

The drugs do have a role in treatment of Alzheimer's patients, but it is a sharply limited one, said Dr. Lon S. Schneider, director of the University of Southern California Geriatric Study Center and author of an accompanying editorial.

"It is almost an important role, but expectations about their effectiveness should be realistic," Schneider said. "They should not be prescribed in the belief that they will keep patients out of nursing homes."

Schneider said he agreed with Gray's negative assessment of company-sponsored trials, because they lack the needed controls.

"Those studies compare patients who are on the drugs and those who are not," he said. "They find that those on donepezil don't go into nursing homes, and they conclude that donepezil is keeping people out of nursing homes. But those taking donepezil might have a more benign version of the condition and might be richer. We don't know if they are staying out of nursing homes because they are taking donepezil or because they have a more benign course of the disease."

Perhaps 90 percent of the Alzheimer's patients treated at USC have been prescribed a cholinesterase inhibitor at one time or another, Schneider said, "but how many of them benefit from it is very uncertain."

A carefully worded statement from the Alzheimer's Association said that "the study should stimulate policy debate and not dictate individual treatment decisions." However, the Association advises that "no one should change an Alzheimer medication regimen, for themselves or a loved one, without careful consultation with their physician," adding that the study "has complex results that will generate wide debate."

More information

You can learn about efforts to treat Alzheimer's disease from the Alzheimer's Association.

(SOURCES: Richard Gray, M.Sc., professor of medical statistics, University of Birmingham, England; Lon S. Schneider, M.D., director, University of Southern California Geriatric Study Center, Los Angeles; Pfizer, Inc., Eisai, Inc., Alzheimer's Association statements; June 26, 2004 The Lancet)

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