MAOIs

Summary

MAO Inhibitors, also called MAOIs, include the drugs tranylcypromine, phenelzine, isocarboxazid, and selegiline. They work by inhibiting MAO enzymes, leading to increased levels of serotonin, norepinephrine, and dopamine. MAOIs are used to treat depression, but due to their side effects and interactions, they are often used as a last resort when other treatments have failed.

Side effects of MAOIs can include CNS stimulation, hypertensive crisis, headache, anticholinergic effects, orthostatic hypotension, serotonin syndrome, nausea, and vomiting. When taking an MAOI, it's important to avoid tyramine-containing foods, SSRIs, tricyclic antidepressants, and many over-the-counter medications. These restrictions need to be continued for at least two weeks after stopping the MAOI.

Key Points

• Monoamine Oxidase Inhibitors (MAOIs)
  • Drug Names
    • Phenelzine (Nardil)
    • Isocarboxazid (Marplan)
    • Tranylcypromine (Parnate)
    • Selegiline (Eldepryl, Zelapar)
  • Mechanism
    • Inhibit monoamine oxidase (MAO) enzymes
      • There are two types: MAO-A and MAO-B
        • Phenelzine, isocarboxazid, and tranylcypromine inhibit both MAO-A and MAO-B
        • Selegiline only inhibits MAO-B
      • Monoamine oxidase is responsible for breaking down neurotransmitters like serotonin, dopamine, and norepinephrine in the brain. Inhibiting this enzyme increases their level in the brain.
        • Increases serotonin levels
        • Increases dopamine levels
        • Increases norepinephrine levels
  • Clinical Use
    • Depression
      • Higher levels of neurotransmitters improve mood and reduce symptoms of depression
      • Used as a last resort
        • MAOIs have so many drug and food interactions that they are not commonly used anymore
        • They will often only be prescribed if other treatments for depression fail
    • Anxiety disorders
      • Generalized anxiety disorder (GAD)
      • Social anxiety disorder
      • Panic disorder
  • Side Effects
    • Hypertensive Crisis
      • A sudden and severe increase in blood pressure that is a medical emergency
      • Can lead to myocardial infarctions, strokes, and and organ damage
    • CNS stimulation
      • Insomnia
        • Take the medication in the morning to prevent sleep disturbances
      • Can also cause anxiety, agitation, restlessness, and mania
    • Headache
    • Orthostatic hypotension
      • Dizziness that occurs from sitting or standing too quickly, due to a sudden drop in blood pressure
      • Teach patients to change positions slowly to avoid falls
    • Nausea and vomiting
    • Anticholinergic effects
      • Includes blurred vision, constipation, dry mouth, difficulty urinating, and drowsiness
    • Serotonin syndrome
      • Can be thought of as a “serotonin overdose” - there is too much serotonin in the synaptic cleft
      • Manifestations include fever, diaphoresis (sweating), tachycardia, tremors, altered mental status, GI distress, and muscle rigidity or spasms
  • Interactions
    • Avoid tyramine-containing foods
      • Hypertensive crisis is often precipitated by consumption of foods that contain tyramine
      • Foods to avoid:
        • Processed meats
          • Pepperoni, salami, bologna, etc.
        • Cheese
        • Red wine
        • Beer
        • Avocados
        • Bananas
        • Raisins
          • As well as other dried fruits
        • Soy
          • Soy sauce, soy beans, tofu etc.
        • Liver
        • Yogurt
        • Caffeine
        • Chocolate
    • Avoid SSRIs and TCAs
      • These drugs alter the level of serotonin in the brain and increase the risk of developing serotonin syndrome
    • Avoid Over-The-Counter (OTC) medications
      • Several OTC medications contain tyramine and could cause hypertensive crisis, while some alter serotonin levels and could cause serotonin syndrome
      • Patient should always consult with their doctor before taking any OTC medication
    • Restrictions should be followed for 2 weeks before and after use of MAOI
      • This applies to all food and medication that interacts with MAOIs
      • When switching to another antidepressant (SSRI, SNRI, TCA, etc.), the patient must be fully tapered off of the MAOI for two weeks before starting the next medication