what is sinemet 12.5? how many milligrams of levodopa are you taking/day?
if that's 12.5mg i doubt you are taking enough to even get any into your brain.
how much requip are you still taking? from what i've read, you normally slowly dose up on sinemet and slowly wean yourself off the agonist.
when were you diagnosed?
how old are you?
what was your first total daily dose of sinemet in milligrams when first prescribed?

just curious, why are you switching?