How Can Diarrhea Due To Aricept Intake Be Treated?

My mother, 89 yrs. old, has dementia and has been on Aricept for 5 months. Started on 5 mg.for 1 mon., then increased to 10 mg. daily. She has had no improvement of dementia symptoms., but has been experiencing extreme diarrhea. She has celiac disease, so is gluten intolerant, so we thought she must be getting wheat somehow, however she is in a facility that provides her food, so she has little access to unapproved food. I think it may be the medication causing her problem. She cannot keep having this problem as she weighs only 100 lbs., having lost 7 lbs this year. Would switching to Namenda eliminate the diarrhea as a side effect?