USED AS ADJUNCT TO LEVODOPA WITH DOPA-DECARBOXYLASE INHIBITOR IN PARKINSON'S DISEASE AND βEND-OF-DOSE' MOTOR FLUCTUATIONS. ENTACAPONE IS AN INHIBITOR OF CATECHOL-O-METHYLTRANSFERASE (COMT). THE MECHANISM OF ACTION OF ENTACAPONE IS BELIEVED TO BE THROUGH ITS ABILITY TO INHIBIT COMT AND ALTER THE PLASMA PHARMACOKINETICS OF LEVODOPA. WHEN ENTACAPONE IS GIVEN IN CONJUNCTION WITH LEVODOPA AND AN AROMATIC AMINO ACID DECARBOXYLASE INHIBITOR, SUCH AS CARBIDOPA, PLASMA LEVELS OF LEVODOPA ARE GREATER AND MORE SUSTAINED THAN AFTER ADMINISTRATION OF LEVODOPA AND AN AROMATIC AMINO ACID DECARBOXYLASE INHIBITOR ALONE.