What is the role of COMT inhibitors in the treatment of Parkinson disease (PD)?

Updated: Jan 24, 2019
  • Author: Robert A Hauser, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Answer

COMT inhibitors inhibit the peripheral metabolism of levodopa to 3-O -methyldopa (3-OMD), thereby prolonging the levodopa half-life and making more levodopa available for transport across the blood-brain barrier over a longer period. Because of the potential risk of hepatotoxicity with tolcapone (Tasmar), liver function test monitoring is required, and this medication should be used only in patients who are experiencing motor fluctuations on levodopa that cannot be adequately controlled with other medications. If dyskinesia occurs, the levodopa dose should be reduced. In patients who already have dyskinesia, the levodopa dose often is reduced by 30-50% at the time tolcapone is introduced.

Entacapone (Comtan) is a COMT inhibitor that does not cause hepatotoxicity; liver function tests are not required with this medication. Levodopa/carbidopa/entacapone (Stalevo) is currently available as a drug combination for Parkinson disease.


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