My wife has been on Donepezil for about 15 months since her diagnosis. It seemed to be working for most of the time but her short term memory has begun to deteriorate rapidly in the last couple of months. She still refuses to accept the diagnosis. She has retained her sense of humour which is good but when she has to put things away she has trouble remembering where they go so now she just leaves them out and I put them away. Sivad