I checked a few drug interaction lists and PD drugs aren't mentioned in the ones I saw. So I tried grapefruit juice with my Sinemet and Mirapex today with no effect. I used Ruby Red grapefruit juice, 100% juice, no sugar added. I wonder if the type of grapefruit juice makes a difference or maybe it's the different meds we're taking. Or like everyone keeps saying, we're all different. Hope it keeps working for you, Ron.