Carbidopa makes the levodopa work better, so you can take less of it. It's one of the drugs in Sinemet. Your doctor may also want you to take dopamine agonist like pramipexole (Mirapex), ropinirole (Requip), or rotigotine (Neupro).
Safinamide (Xadago) is an add-on medicine that your doctor may prescribe when you're taking levdopoa and carbidopa and have a breakthrough of symptoms that used to be under control.
When you take levodopa, a chemical in your body called COMT makes part of the drug useless. Entacapone (Comtan) and tolcapone (Tasmar) block COMT, so the brain can use levodopa more effectively.