carbidopa/levodopa

An orally available combination of carbidopa, an inhibitor of aromatic amino acid decarboxylation, and levodopa, an inert, metabolic precursor to dopamine, with dopaminergic and antiparkinsonian properties. Upon oral administration, levodopa crosses the blood-brain barrier (BBB) and is decarboxylated to dopamine via dopa decarboxylase in the brain, promoting increased activation of dopamine receptors. Carbidopa inhibits dopa decarboxylase in the periphery, thereby preventing decarboxylation of levodopa in extracerebral tissues and increasing the delivery of dopamine to the central nervous system (CNS). As carbidopa does not cross the BBB, it does not interfere with CNS levodopa metabolism.