Dear Mary,
This is hard when this starts to happen, because many of the drugs to treat Parkinsons can cause other problems with the LBD, Many try the "Sinimet" but in small doses,I am sure you have a Dr who is well aware of LBD and its effects I am adding a link from Yahoo for an over view look at this drug, I hope it helps and Good Luck to you and your Dad!
When you get there read the overview and then click link to different type's of Dementia's. Interesting reading!
http://health.yahoo.com/topic/nervous/o ... 5kYtlLvs8F