Disclosing this to reporters on Thursday, Dr Ravi Anand, global head of the Central Nervous System, Novartis, which developed the drug, said the company has launched an extensive experiment to ascertain the reasons for the interesting finding. Covering 13 countries, the study will look into the impact of hypertension in the treatment using Exelon.

He said Exelon, which was launched in India in February, has been found to be effective in slowing down the deterioration rate in AD patients, irrespective of the disease stage. About 60 per cent of patients in advanced stages showed overall improvement using Exelon, while 80 per cent became less indifferent than before treatment.

Alzheimer's disease, which literally drills holes in thecerebral cortex, is caused due to deficiency of a neurotransmittor called acetyl choline.