Benserazide
Benserazide is an inhibitor of DOPA decarboxylase that does not enter the central nervous system. It is often given with L-DOPA (levodopa, 3,4-dihydroxy-L-phenylalanine) in the treatment of Parkinson's disease to prevent the conversion of L-DOPA to dopamine in the periphery, thereby increasing the amount that reaches the central nervous system and reducing the required dose. It has no antiparkinson actions when given alone.