Memantine and Donepezil. Do any of you have experience with these drugs?

Those drugs were tested in much younger patients than your dad. In my opinion, the side effects are not worth it given his age. Sleeping, eating, and not being in pain with cramps aren't too much to want for him to have for however long he has left to live.

I took dad off the donezepil after expressing my concerns to his doctor. The side effects weren't worth it. He lost appetite (and he's already frail) and was more wobbly. So far I've kept him on the other drug (memantine) but I certainly don't see any effects of it one way or the other.

My DH aunt, 94, has taken both drugs for several years. She started with Aricept. She was having problems with her stomach and we stopped the Aricept for awhile until we got her gastro issues resolved. She was put back on the Aricept and did fine. A couple of years later the Namenda was added.
I have discussed with her and her doctors more than once on next steps regarding continuing taking or stopping the drugs. We have always decided to continue as she has progressed very slowly with her dementia.
She was first prescribed the Aricept by her primary. Then a neurologist prescribed along with the Namenda. Then her geriatrics doctor suggested she stay on them. Now she is on hospice and still takes them. In fact the hospice supplies them for her.
She has been lucky in that they appear to help her. It is difficult to know for sure. If they made her sick, I would discontinue.
I have heard others say it’s not effective after a certain length of time and I have tried to find that information on various websites to confirm that. I have never been able to confirm it. Since DH aunt was seeing a highly regarded geriatric primary associated with a major teaching hospital I decided to follow her recommendation and leave aunt on the meds. I fully expected the hospice doctor to take her off of it. Instead they took over the cost and are supplying it.
I know it’s difficult to make these decisions. I would not take him off without consulting his doctor as he may need to taper the dosage and not stop all at once.

I take care of my MIL with mild Alzheimer’s. She is for 7 months on memantine now and recently donezepil was added. It’s hard to know if the medication does anything, it’s not to “measure”
When I had to add the donezepil, half the dose for 2 weeks to start with, after a few days she got nasty side effects. Insomnia and nightsweats, among with a few that where less severe appeared. After two weeks we contacted the neurologist. As her family caregiver I discussed it with my SIL and of course with my MIL herself. MIL wanted to quit, she was a wreck over the lack of sleep and the draining nightsweats. After research we saw that the donezepil might only work for 6 months to begin with. Adding the other half of the pill with more side effects in the make that might not disappear at all we decided to stop the donezepil. In the first place because MIL wanted it herself, she needs to be heard. Thereby, we promised her to go for comfort along this road.
We did talk it through with the neurologist and he fully agreed.
Go with your gutfeel. For us her comfort is put on one. Nothing wrong with giving something a try but till a certain level.

Those two drugs are about all that is FDA approved for AD and often they are prescribed together. They are suppose to slow down the symptoms but I didn't see that in my wife. I thought it was money down the drain so I discontinued them myself. In addition, for those who do take the drugs and see some benefit, they are only effective for a short period of time, maybe 12-18 months. So at his age, I think you can make the call.