What do you think?
From my negative experience of Sinemet, I surmise that it brings some initial improvement in movement issues along with some devastating side effects. It wears off, so more is taken, and after a while dyskinesias can occur solely because of the drug. Also 'on - off' can occur due to the drug.
Eventually it loses its effectiveness completely (which is a separate thing from PD progression), so the pwP is addicted to it, but with no benefit, and probably still getting side effects.
Outraged that this 50 + year old drug is still used, despite what I understand to be decades of research and the promise of a 'jam tomorrow' breakthrough, which is always in '5, 10 or 15 years'.