We have a booklet called Drug treatments for Parkinson's that you can download from this website. It has information on the side effects of various Parkinson's drugs. In fact, it does mention nausea and vomiting as some of the more common side effects.
Do have a look at the booklet and if you have further questions, you can post them here or contact our helpline team at email@example.com.
If I take Sinemet without food I feel sick and have to lay down, if I take it with food I'm OK. I had similar side effects (and many others!) but far, far worse when I was taking Ropinirole.