<P> With L - DOPA identified as the active form, Alfred Pletscher and his colleagues at Hoffman - LaRoche synthesized benserazide, an inhibitor of DOPA decarboxylase, which further reduced the required dose . A drug combining L - DOPA with benserazide was marketed under the brand name of Madopar . Independent work was carried out by Victor Lotti at Merck in West Point, Pennsylvania . Merck had already synthesized and patented carbidopa, another dopa decarboxylase inhibitor in 1962, and in 1971 Lotti showed that the use of the L - form of carbidopa, further reduced the therapeutic dose of L - DOPA . The combination of L - carbidopa and L - DOPA was marketed under the brand name of Sinemet . </P> <P> It is available as a generic medication and is moderately expensive . Globally, the wholesale price of the medication is about 1.80 to 3.00 USD a month . In the United States a month's supply is about 50 to 150 USD . </P> <Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2015) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2015) (Learn how and when to remove this template message) </Td> </Tr>

What is the mechanism of action of carbidopa