New research shows that patients with severe forms of Alzheimer’s disease who stayed on dementia drug Aricept (donepezil), approved only to treat mild to moderate forms of the disease, for longer had slower memory decline compared to patients who were given placebo tablets.

Researchers also found that Namenda (memantine), another commonly distributed dementia drug in the U.S. were also beneficial for patients with severe Alzheimer’s, although the effectiveness was more modest compared to Pfizer’s Aricept.

British scientists suggest that extending Aricept treatment to more people for longer may significantly reduce cognitive decline in Alzheimer patients and suggest that the latest findings could lead to twice as many Alzheimer’s patients worldwide to be given the medications because cheaper generic versions of donepezil and memantine will soon be made available as both drugs lose their patent rights.

The study, published in the March 8th edition of the New England Journal of Medicine, consisted of 295 Alzheimer's patients in England and Scotland who had already been taking Aricept who were divided into four groups. Participants were either given a placebo, Aricept, Namenda (memantine), a drug prescribed only in later stages of Alzheimer’s, or a combination of Aricept and Namenda.

Researchers then evaluated each group’s cognition scores on memory and ability to cope with everyday tasks like dressing and eating for a year.

Researchers found that while the drugs were unable to completely stop the mental decline in patients, the medication had significantly slowed their mental deterioration.

The results demonstrated that continuing Aricept treatment gave benefit over taking the placebo, and switching to Namenda provided less benefit than staying on Aricept alone. Researchers did not find evidence that the combination of the two drugs provided significantly more benefit over taking Aricept by itself.

"We observed that patients who continued taking donepezil were better able to remember, understand, communicate, and perform daily tasks for at least a year longer than those who stopped taking the drugs. These improvements were noticeable to patients, their caregivers, and doctors," lead author Dr. Robert Howard of the Institute of Psychiatry at King’s College London said in a statement.

However, a separate analysis indicated that each drug had an independent benefit, so Howard recommended that doctor prescribe a combination of Aricept and Namenda if possible to patients with moderate to severe Alzheimer’s.

"For the first time, we have robust and compelling evidence that treatment with these drugs can continue to help patients at the later, more severe stages of the disease," Howard said in a statement.

"As patients progress to more severe forms of Alzheimer's disease, clinicians are faced with a difficult decision as to whether to continue or not with dementia drugs, and until now, there has been little evidence to guide that decision," he added.

However in an accompanying editorial, Dr. Lon Schneider said while the results showed the potentially important results the findings “should not be interpreted as evidence of the efficacy of indefinite treatment with the drug,” and more research is needed to determine the long-term benefits, the potential for harm and physiological tolerance, and the safe discontinuation of cholinesterase inhibitors as Alzheimer's disease progresses.

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