Bed bound & aggressive -looking for advice

Leadlines

I'm new here and looking for advice. A little background -I help care for my 84 year old father. He has late stage Alzheimer's, bed bound and completely dependent for care. Communication is difficult as his eyesight and hearing are poor and his ability to speak coherently is mostly gone.
We are having a terrible time with diaper changes, every time. He fights constantly, yelling, trying to bite and hit. It takes 2 to 3 people to get him changed. We wait the appropriate amount of time after his 4 medications which are supposed to keep him calm, we explain what we need to do in detail (showing him a new diaper, touching the one he's wearing, asking if we can change him, and he'll say yes). Is anyone else going through this struggle? I can't find any information/guidance on dealing with this type of situation. Outside of diaper changes he is usually well behaved and easy to care for. I never thought I'd have to tell my own father not to bite me.