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Monoamine oxidase-B (MAO-B) is an enzyme in the body that breaks down several chemicals in the brain, including dopamine. An MAO-B inhibitor makes more dopamine available to the brain. This can modestly improve many PD movement symptoms.

MAO-B inhibitors may be useful as early monotherapy (a medication used alone) or as an add-on to other medications, including levodopa. When used with other medications, MAO-B inhibitors may reduce motor fluctuations periods of diminished symptom control as a levodopa dose wanes minimizing “off” time and extending “on” time.

Quick Facts

  • MAO-B enzymes naturally break down several chemicals in the brain - including dopamine - making dopamine more available.
  • These drugs can provide modest benefits for Parkinson’s movement symptoms.
  • Such medications are can be used early in the disease as monotherapy or as an adjunct (add-on) to other medications.
  • When used together with other medications, MAO-B inhibitors may reduce “off” time and extend “on” time.

Forms of MAO-B Inhibitors

Common Side Effects of MAO-B Inhibitors

  • Mild nausea
  • Dry mouth
  • Lightheadedness
  • Constipation
  • Confusion (can occur in elderly people with PD)
  • Hallucinations (can occur in elderly people with PD)

Potential for Neuroprotection

Animal studies have historically suggested that MAO-B inhibitors might slow the progression of Parkinson’s, offering neuroprotection. When tested in humans true disease modification remains unproven.

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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