My Husband Have Been Taking Aricept 5mg For A Number

My husband have been taking Aricept 5mg for a number of years. Then it was increased to 10mg for a couple of years. On July 14, 2015 it was increased to 20mg, which has caused severe diarrhea. Calling the doctor, he said to cut it down to 10mg for a couple of days, then increase to 20mg. The diarrhea is so severe that it causes his ansus to bleed. If he stops the Aricept will it cause serious side affects?