Sinemet without Parkinson's

Hi,

Does anyone know what effects Sinemet has on someone who doesn't have Parkinson's? It's never been clear that my dad has Parkinsons; but he has been prescribed this med anyway...at a very high now. It doesn't help his balance at all, and has made him almost impossible to live- rude, self absorbed, impulsive. He has given up all his activities and sits around all day eating like crazy.

This doesn't seem consistent with what others have said their experience with Sinemet has been. Has anyone else seen such a change with someone on this med?