Levodopa is converted to dopamine in the brain. Carbidopa helps prevent the breakdown of levodopa before it can reach the brain and take effect. Carbidopa and levodopa enteral (Duopa) is a combination medicine used to treat movement problems in people with advanced Parkinson's disease. Duopa reduces the "off time" effect associated with taking other medicines to treat Parkinson's symptoms. Duopa is a gel form of carbidopa and levodopa that is infused directly into the small intestine. This medicine is given with an infusion pump through a tube inserted into the wall of your stomach through a surgical incision called a "stoma" or a "port." Carbidopa and levodopa may also be used for purposes not listed in this medication guide.