Carbidopa

Carbidopa, sold under the brand name Lodosyn, is a medication used primarily in the treatment of Parkinson's disease. A DOPA decarboxylase inhibitor, Carbidopa blocks the enzyme aromatic L-amino acid decarboxylase (DDC) in the peripheral nervous system, preventing the premature conversion of levodopa to dopamine outside the brain. Because carbidopa cannot cross the blood-brain barrier, it has no effect on DDC activity within the central nervous system, allowing a greater proportion of co-administered levodopa to reach the brain intact.