Aromatic L-amino acid decarboxylase inhibitor

An aromatic L-amino acid decarboxylase inhibitor (synonyms: DOPA decarboxylase inhibitor, extracerebral decarboxylase inhibitor, DDCI and AAADI) is a medication of type enzyme inhibitor which inhibits the synthesis of dopamine by the enzyme aromatic L-amino acid decarboxylase (AADC, AAAD, or DOPA decarboxylase). It is used to inhibit the decarboxylation of L-DOPA to dopamine outside the brain, i.e. in the blood. This is primarily co-administered with L-DOPA to combat Parkinson's disease. Administration can prevent common side-effects, such as nausea and vomiting, as a result of interaction with D₂ receptors in the vomiting center (or cheomoreceptor trigger zone) located outside the blood–brain barrier.^[2]

Examples of extracerebral decarboxylase inhibitors include carbidopa and benserazide.

Peripherally selective DDCIs 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 conversion of L-DOPA into dopamine outside the brain, for the purpose of reducing adverse side effects.^[3] Combined L-DOPA and DDCI therapy does not inherently decrease peripheral cardiovascular side effects of L-DOPA administration; however, combined therapy potentiates the central effects of L-DOPA by decreasing the dose-dependency 4-5 fold, therein allowing for effective Parkinson's disease treatment without cardiovascular risk associated with high peripheral dopamine.^[4][5]

• Benserazide (Madopar, Prolopa, Modopar, Madopark, Neodopasol, EC-Doparyl, etc.)
• Carbidopa (Lodosyn, Sinemet, Pharmacopa, Atamet, Stalevo, etc.)
• Methyldopa (Aldomet, Aldoril, Dopamet, Dopegyt, etc.)
• alpha-Difluoromethyl-DOPA (DFMD)
• 3',4',5,7-Tetrahydroxy-8-methoxyisoflavone [58262-89-8]
• Epigallocatechin gallate (EGCG)
• Epigallocatechin (EGC)