COMT inhibitors like entacapone and tolcapone are only given with levodopa to prevent the enzyme from breaking it down outside the central nervous system, thus allowing more of it to enter the brain.

COMT抑制剂，例如恩他卡朋和托卡朋与左旋多巴一起用于治疗，只是为了防止左旋多巴在中枢神经系统外被分解，从而使更多左旋多巴进入脑中。