NAPLEX Practice Question # 30

NAPLEX Examination.

Practice Question # 30.





COMT inhibitors

  1. Tolcapone (Tasmar)

Mechanism of action

  • Tolcapone is a selective and reversible inhibitor of COMT and is used as an adjunct to levodopa/carbidopa therapy.
  • Tolcapone inhibits COMT both peripheral and centrally.
  • COMT is the main enzyme responsible for peripheral and central metabolism of catecholamines, including levodopa. Addition of a COMT inhibitor results in the doubling of the elimination half-life of levodopa and in increased oral bioavailability of levodopa by 40% to 50%.
  • Tolcapone is indicated as an adjunct therapy to carbidopa/levodopa therapy.

Administration and dosage

  • Starting dose of 100 to 200 mg three times daily
  • Usual daily dose of 200 mg three times daily
  • c) If patient fails to show expected benefi t aft er 3 weeks of treatment, discontinue drug because of associated risk of liver failure. Rapid withdrawal or abrupt reduction dose could lead to hyperpyrexia and confusion symptoms such as high fever and severe rigidity similar to those in neuroleptic malignant syndrome.

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