I don't know about Parkinson's patients taking coumadin, I just know that it can be very dangerous if not monitored carefully. My husband (37 at the time) had a slight stroke and was put on coumadin for six months. For the first 2 months he was on it, he was monitored with blood tests, at first 2 - 3 times weekly, then at least once bi-weekly to make sure he was not getting too much. If the blood gets too thin, it can create a very dangerous situation. Is she being monitored closely? I know they changed the dosage for my husband at least twice a week for about 3 weeks until they got it right. Hope this helps. Wendy (CG for Ruth 77/4+)