The decarboxylase inhibitor that is co-administered with levodopa in Madopar

Benserazide is an inhibitor of DOPA decarboxylase that does not enter the central nervous system. It is often given in combination with L-DOPA (levodopa) as Co-Beneldopa (BAN) (e.g. Madopar® by Roche in UK) in the treatment of Parkinson's disease to prevent the conversion of L-DOPA to dopamine in the periphery (due to its molecular size it can not penetrate the blood brain barrier) the amount that reaches the central nervous system and reducing the required dose, and also decreasing side effects due to the presence of dopamine in the system (outside of the central nervous system).