But the shocking results show that about eleven patients have died while taking Aricept during a clinical trial held at Japan's Eisai Co.
There were no deaths among patients who were taking a placebo. This news would lead to calls for greater scrutiny of clinical trials.
David Windley, an analyst at Jefferies quoted that the deaths were among 648 patients who received Aricept once daily for 24 weeks. There were no deaths in the 326 patients receiving placebos.
The Eisai trial is a Phase 3 study, the final period of testing before companies present proposals to regulators for approval. Sam Gandy, chairman of medical and scientific advisory council of the Alzheimer's Association, said that it was a rather surprising result but the findings cannot negate 10 years of the drug's safety record on the market.
Gandy, who is also director of the neuroscience institute at Thomas Jefferson University in Philadelphia, said that patients taking Aricept in the latest trial showed a statistically significant improvement in cognitive function, compared with those taking placebos.
On the other hand the drug is approved for vascular dementia in a number of smaller markets, including South Korea and India.