Carbidopa/levodopa, also known as levocarb and co-careldopa, is the combination of the two medications carbidopa and levodopa.[1] It is primarily used to manage the symptoms of Parkinson's disease but does not change the course of the disease.[1] It is taken by mouth.[1] It can take two to three weeks of treatment before benefits are seen.[2] Each dose then begins working in about ten minutes to two hours with a duration of effect of about five hours. Common side effects include movement problems and nausea.[1] More serious side effects include depression, low blood pressure with standing, sudden onset of sleepiness, psychosis, and increased risk-taking behavior.[1][5] Carbidopa prevents the breakdown of levodopa outside the brain.[5] In the brain, levodopa is broken down into dopamine by which it has its effects.[5] Carbidopa also helps prevent some of the nausea which levodopa causes.

It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.[7] It is available as a generic medication and is moderately expensive.[5] The wholesale price in the developing world is about US$1.80 to $3.00 a month.[8] In the United States, a month's supply costs about $50 to $150.[1] In 2017, it was the 184th most commonly prescribed medication in the United States, with more than three million. It is primarily used to improve the symptoms of Parkinson's disease but does not change the course of the disease.[1] It can take two to three weeks of treatment before benefits are seen.[2] Each dose then begins working in about ten minutes to two hours depending on the formulation, with a duration of effect of about five hours.