Carbidopa/levodopa

Carbidopa/levodopa, sold under the brand name Sinemet among others, is a fixed-dose combination used for the treatment of Parkinson's disease. It contains carbidopa, an inhibitor of aromatic amino acid decarboxylation; and levodopa, an aromatic amino acid. It is taken by mouth.

Common side effects include movement problems and nausea. More serious side effects include depression, low blood pressure with standing, sudden onset of sleepiness, psychosis, and increased risk-taking behavior. Carbidopa prevents the breakdown of levodopa outside the brain. In the brain, levodopa is broken down into dopamine – its active form. Carbidopa also helps prevent some of the nausea which levodopa causes.

It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2023, it was the 310th most commonly prescribed medication in the United States, with more than 200,000 prescriptions.