Hallo Bidle,
I'm sorry your mum is having such a bad time - and of course the knock-on effect you and your dad is awful too.
My mum became very paranoid, convinced that a neighbour was out to get her. It was her only topic of conversation, despite our best attempts to distract her, she would pace around all day, constantly check locks, push furniture against doors, and couldn't sleep at night, begging to be taken away to somewhere safe.
I took the view that if things went on like this then frankly her life wasn't worth living - there was no pleasure or even peace in it - so going with anti-psychotics felt like an easy decision to me. Of course there are some risks - but so there are to some extent with any drug. It took a while to find an anti-psychotic which worked for her - the first two that were tried (quetiapine and olanzapine) made no difference to her at all. Then she was put on risperidone and I am happy to say that this has removed all her paranoia. At last she is relaxed and content and we have been able to start doing some of the things that she enjoys again, like going out to singing.
She has been on this for 6 months now and there have been no obvious or severe side effects. She is more unsteady on her feet, but that was becoming a problem before she started taking the pills, so that may just be natural progression of the dementia. She is a little quieter, but is certainly not a zombie and can still have sensible conversations on good days. In fact better than before because the subject does not always go straight back to the neighbour!
As I say, I did not have any doubts that anti-psychotics were worth a try. I had more trouble trying to get the consultant to prescribe them. I'm not sure if he just wanted to be sure that I wouldn't blame him if mum did have a stroke, but I assured him that I understood the risks and thought that mum's distress was such that there was no quality of life there.
Have you talked to your dad about this? What does he think? It must be so hard for him if your mum is not recognising him as someone who loves and cares for her. Nevertheless, he may find it more difficult than you to accept the risk on his wife's behalf. I can only say that, based on my experience with my mum, I think they are worth trying.