n. a U.S. trade name for a drug combination of levodopa and carbidopa used in the treatment of Parkinson’s disease, the symptoms of which are due to lack of striatal dopamine. Carbidopa inhibits the action of the enzyme dopa decarboxylase in peripheral tissues, thereby enabling levodopa to be administered in lower doses to achieve an effective concentration in the brain, where it is converted by striatal enzymes into dopamine.