A DOPA decarboxylase inhibitor (DDCI) or aromatic L-amino acid decarboxylase inhibitor (AAADI) is a type of drug which inhibits the metabolism of dopamine by the enzyme aromatic L-amino acid decarboxylase (AAAD) or DOPA decarboxylase (DDC).
Peripheral DDCIs which are incapable of crossing the protective blood-brain-barrier (BBB) are used in augmentation of L-DOPA (Levodopa) in the treatment of Parkinson's disease (PD) to block the peripheral conversion of L-DOPA into dopamine for the purpose of reducing adverse side effects.
^ "Editorial: Dopa decarboxylase inhibitors". British medical journal 4 (5939): 250–1. November 1974. PMID 4425849.