My mother has been on varying doses of cogentin for 4 years. At this time, she is on her lowest dosage, one pill a day. It seems to help her shaking more than giving her extra sinemet. The worst side effect we have seen are her hallucinations. They can be rather scary. At one time, she was on 4 doses a day--far too much and not necessary. However, we discovered that it was the stress and sadness of losing our father and her husband that caused her so much discomfort that only that much could help her. We did wean her off of it completely a year ago, but after falling and breaking her hip in May we found that putting her back on it was a great help. She is 79 and has had PD for 25 years. Hope this helps. Laurie Cook