Carbidopa/levodopa

Carbidopa/levodopa is a fixed-dose combination medicine taken by mouth for Parkinson's disease, sold under brand names such as Sinemet. Levodopa is converted into dopamine in the brain, which relieves the tremor, stiffness and slowness of movement that come from dopamine loss, while carbidopa blocks the breakdown of levodopa outside the brain. That lets a lower dose of levodopa be used and reduces the nausea and vomiting it would otherwise cause. It improves symptoms but does not change the course of the disease. The history runs from Oleh Hornykiewicz's 1960 finding that dopamine was reduced in the brains of people who died with Parkinson's disease, through George Cotzias's high-dose levodopa work in 1967, to Merck's patented carbidopa and Victor Lotti's 1971 demonstration that the L-form of carbidopa lowered the effective dose. The combination is on the World Health Organization's List of Essential Medicines, is available as a generic, and has been sold in immediate-release, extended-release and intestinal infusion forms.