Carbidopa and levodopa is a combination medicine used to treat symptoms of Parkinson's disease, such as muscle stiffness, tremors, spasms, and poor muscle control. Parkinson's disease may be caused by low levels of a chemical called dopamine (DOE pa meen) in the brain. 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 is also used to treat Parkinson symptoms caused by carbon monoxide poisoning or manganese intoxication. Carbidopa and levodopa may also be used for purposes not listed in this medication guide.