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MAO-B inhibitors

What are the Facts?

  • MAO-B is an enzyme in our brain that naturally breaks down several chemicals in our brain including dopamine.
  • MAO-B inhibitors help to block the break down of dopamine in the brain, thus making more dopamine available and reducing some of the motor symptoms associated with PD.
  • The MAO-B inhibitor Selegiline was previously thought to be neuroprotective, meaning that it could stop the death of dopamine-producing neurons and delay the progression of symptoms in PD.
  • Early studies of  the second-generation MAO-B inhibitor rasagiline (Azilect®) showed that 1 mg per day had benefits consistent with the possibility that the drug has a disease-modifying effect which slows disease progression.  While larger doses showed no such effect, if this can be confirmed, this would be the first drug determined to have a disease modifying effect in PD.
  • Today, neurologists agree that MAO–B inhibitors provide modest improvements in early disease and adjunctively enhance dopaminergic function later in the disease.
  • MAO-B inhibitors are usually used as early monotherapy or as an add-on medication to drugs such as levodopa in more advanced PD to decrease “off” time.

The MAO-B inhibitors selegiline (Eldepryl®) and Rasagaline (Azilect) enhances the effect of levodopa:

Selegiline is available in two formulations:

  • Standard oral—converted into an amphetamine like by-product, which may contribute to side effects of jitteriness and confusion.
  • Orally-disintegrating (Zelpar®) – preferred form for people with PD who have difficulty swallowing.


Rasagiline is available in 0.5mg and 1mg doses:

  • The MAO-B inhibitor rasagiline (Azilect® ) is generally given in 1 mg doses once a day.   Two studies (LARGO and TEMPO) have shown that it can reduce wearing off in Levodopa treated patients.
    Recent studies have led to the reclassification of these medications as highly selective MAO-B inhibitors. Food restrictions have been relaxed by the FDA. However, there may be contraindications with other prescription medications, vitamins, over the counter cold pills, and homeopathic remedies. Anyone taking a PD medication should talk to their doctor and pharmacist about potential drug interactions. 

What are the Side Effects?

  • Mild nausea
  • Dry mouth
  • Lightheadedness
  • Constipation
  • Confusion (can occur in the elderly person with PD)
  • Hallucinations (can occur in the elderly person with PD)
  • In Monotherapy Rasagaline Dopaminergic side effects were very similar or better than Placebo.

Caution: PD medications may have interactions with certain foods, other medications, vitamins, herbal supplements, over the counter cold pills and other remedies.  Anyone taking a PD medication should talk to their doctor and pharmacist about potential drug interactions.

Page reviewed by Dr. Joash Lazarus, NPF Movement Disorders Fellow, Department of Neurology at Emory University School of Medicine.