I've been dealing with this for months and she was doing fine on Ambien and then all of a sudden started hallucinating at night. Before the Ambien I was using a combo of herbs to include melatonin. So I've gone back to that in higher doses but then all of a sudden they won't work either. I've tried 50mg of Trazodone which didn't work so gave her another half and it sort of worked. She is sensitive to drugs - she either has a horrible reaction or needs a lot of it to work. She cannot tolerate most anti-depressants or any drug of that class. She only takes a blood pressure medication and carbi/levodopa and supplements. Someone recommended seroquel but I am concerned about the drugs because she doesn't tolerate them very well for very long. I can't be up all night like this 3 or 4 times a week.
I was in this situation with my husband. Seroquel saved us. It remained effective at the same dose for the whole 9 years he took it. He had Lewy Body Dementia, which is related to Parkinson's. If you decide to try it, make sure it is the only drug added (until it is stable in her system), that you start at a low dose and gradually move up to a therapeutic dose, and watch for side effects. If it doesn't work for her, you can reverse the process and gradually decrease the dose.
Benadryl can be an effective sleep aid, but as FF says, don't start it without a doctor's OK. And I'd add that the doctor who OKs it should be a specialist. I know that benadryl is NOT recommended for persons with LBD, and since that is related to Parkinson's I'd want a specialist's opinion before giving it to Mom.
What is Mother like when she wakes up? Do you know if she flails her arms or legs in bed? Does she seem to be acting out a dream? The REM Sleep Behavior Disorder (RBD) is associated with Parkinson's and with Lewy Body Dementia, and there is a very effective treatment for that. It can be diagnosed with a sleep study.
Someone told me that Seroquel is a "big gun for a little problem." But frequent night awakenings are NOT a "little problem" -- not when it disturbs the caregiver's sleep. It can literally be the factor that allows keeping a loved one out of a care center. I wish you lots of success in solving this, with or without Seroquel.
Do let us know what you try and how it works for you. We learn from each other.
Anytime I want a good night sleep I use the over the counter Benadryl, which is used mainly as an allergy medicine but is also used to induce sleep and also for Parkinson's [the later surprised me]. I don't use it every night otherwise I feel like I am a fog the next day. Check first with your Mom's doctor to see if she could take this medicine since she is taking blood pressure medicine.