Ibby, if you are taking sinemet or any form of l-dopa, avoid any medication containing l-tyrosine. Ron Hutton learned this the hard way. When he was supplementing with tyrosine he experienced unpredictable, hard off periods. Discontinuing the tyrosine solved the problem.
There is a thread about three weeks ago on this. I don't know how to post a link to that thread. Maybe I can find it and bump it up.