Closeup shot of pharmacists putting medicine in a bag

This class of Parkinson’s disease (PD) medications has little to no direct effect on symptoms but is used to prolong the effect of the Parkinson’s medication levodopa by blocking its break down. Catechol-O-methyl transferase (COMT) inhibitors are used primarily to help with “wearing off changes in the ability to move as the effect of levodopa becomes short-lived.

Quick Facts

  • Catechol-O-methyl transferase (COMT) is a body enzyme. When a person takes levodopa, COMT can deactivate levodopa before it enters the brain and central nervous system; COMT inhibitors prevent this from happening.
  • COMT inhibitors are most effective when used in combination with levodopa to extend “on” time.

Forms of COMT Inhibitors

Common Side Effects of COMT Inhibitors

  • May exaggerate some levodopa-related side effects, especially dyskinesia
  • Confusion
  • Hallucinations
  • Discoloration of urine (reddish brown or rust-colored)
  • Diarrhea

Page reviewed by Dr. Chauncey Spears, Clinical Assistant Professor and Dr. Amelia Heston, Movement Disorders Fellow at the University of Michigan.

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