What are MAO-B inhibitors?
MAO-B (monoamine oxidase-B) inhibitors are a class of medications that are used to treat the symptoms of Parkinson’s disease (PD). While carbidopa-levodopa therapy is the most effective medication available to treat the motor symptoms of PD, some people are also prescribed additional medications to manage their symptoms, like MAO-B inhibitors. MAO-B inhibitors may be used alone in early stages of PD, or they may be used in combination with other treatments, like carbidopa-levodopa therapy. MAO-B inhibitors have been shown in clinical trials to have a modest effect on relieving the symptoms of PD.1,2
MAO-B inhibitors may reduce the motor fluctuations seen in many people with PD. People treated with carbidopa-levodopa often experience fluctuating symptoms of PD and are described as having “on” and “off” episodes. “On” episodes are experienced when medication is working and symptoms are minimal, and “off” episodes are when the medication hasn’t yet taken effect or is wearing off and symptoms are worsened. “Off” episodes can interfere with daily activities and may be experienced multiple times a day. They may last a few minutes or as long as a few hours.1,2
How MAO-B inhibitors work
MAO is an enzyme found throughout the cells in the body. There are two types of MAOs: MAOs in the intestines are predominantly type A, while most of the MAOs in the brain are type B. In the brain, MAO-B plays an important role in the breakdown of neurotransmitters (chemical messengers) like dopamine. MAO inhibitors (MAOI) block the action of the enzyme.3
The motor symptoms of Parkinson’s are caused by the reduction in dopamine, which transmits signals in the brain to produce smooth, purposeful movement. As PD damages and destroys the neurons (nerve cells) that produce dopamine, the motor symptoms of PD appear. Levodopa therapy provides the precursor to dopamine – it is the substance that is used to make dopamine. Adding an MAO-B inhibitor slows the breakdown of levodopa and dopamine in the brain, and may boost the effect of levodopa.1
Formulations of MAO-B inhibitors
There are several different formulations of MAO-B inhibitors, including:
- Eldepryl® (selegiline hydrochloride)
- Carbex® (selegiline)
- Zelapar® (selegiline hydrochloride, orally disintegrating tablet)
- Azilect® (rasagiline)
- Xadago® (safinamide, tablets)
- Emsam® (selegiline patch)1
Side effects of MAO-B inhibitors
Each medication has its own set of possible side effects. Selegiline (found in Eldepryl, Carbex and Zelapar) may cause dizziness, headache, confusion, nausea, insomnia, dyskinesia (uncontrolled, abnormal movements), and agitation. Rasagiline (found in Azilect) may cause increased dyskinesias (uncontrolled, abnormal movements), orthostatic hypotension (falling blood pressure that occurs upon standing), headaches, joint pain, and indigestion.1,2
MAO-B inhibitors may cause serious side effects when taken with other medications, such as antidepressants, selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants. Also, there may be interactions with certain foods when taking this class of drug. People taking MAO-B inhibitors should discuss with their doctor all medications they are taking along with their regular diet.4
Note that this list of side effects is not a complete list, and people with PD should talk with their doctor to learn more about the side effects of each medication.
It is important that people with PD see a movement disorder specialist, who is specifically trained in treating PD and understands the role of medications, including which drugs may worsen symptoms.1 It is also important to talk with your healthcare provider before starting or stopping any new treatments, including over-the-counter medications and alternative treatments.
Besides MAO-B inhibitors, there are several different types of treatment for the symptoms of PD, including carbidopa-levodopa therapy, dopamine agonists, anticholinergics, and surgery for deep brain stimulation. Each person with PD experiences a highly individual set of symptoms and progression of the disease. Treatments are determined based on the individual’s symptoms and how they respond to different medications.