Monoamine Oxidase Inhibitors

Monoamine oxidase inhibitors (MAOIs) include isocarboxazid (Marplan), phenelzine (Nardil), and tranylcypromine (Parnate). These medications are rarely used because of strict dietary requirements and life-threatening drug and food interactions. Because of these drug and food interactions, MAOIs may not be taken with many other types of medicines, and some foods that are high in tyramine, dopamine, or tryptophan must be avoided as well.

How do MAOIs work?

These drugs inhibit monoamine oxidase. Monoamine oxidase is an enzyme in the body that is responsible for metabolizing (breaking down) neurotransmitters such as norepinephrine, epinephrine, dopamine, and serotonin. The result of MAOIs is an increase in the concentration of neurotransmitters. Some of these neurotransmitters increase blood pressure.

Who should not use these medications?

In many circumstances, the use of MAOIs is dangerous.

• Individuals who are allergic to MAOIs



• Individuals with diseases, such as pheochromocytoma or hypertension, that cause increased blood pressure



• Individuals with diseases, such as heart failure or other heart disease, severe impaired renal function, and stroke or other cerebrovascular disease, in which increased blood pressure is likely to aggravate the condition



• Individuals with a history of headache



• Individuals with liver disease



• Individuals using other drugs that may elevate blood pressure or cause additive effects (see drug interactions)



• Individuals consuming foods with high tyramine content—MAOIs may lead to dangerously elevated blood pressure (see food interactions)

• MAOIs are administered orally.



• MAOIs are rarely the first antidepressant drug prescribed, but they are an option when initial treatments do not work or are not tolerated.



• MAOIs are not a good choice for elderly or debilitated individuals.

Children: Phenelzine is not approved for children younger than 16 years. Tranylcypromine is not approved for children or adolescents.

Drug or food interactions: Tell the doctor what medications are currently being taken because many drugs interact with MAOIs. Do not take any nonprescription or herbal medications without first consulting the doctor or pharmacist. The following are examples of interactions, but they do not represent a complete list.

• The risk for serotonin syndrome may be increased by SSRIs, TCAs, atomoxetine (Strattera), duloxetine (Cymbalta), dextromethorphan (in many cough syrups), dexfenfluramine, 5-HT1 agonists [such as sumatriptan (Imitrex) or zolmitriptan (Zomig)], venlafaxine (Effexor), St. John's wort, or ginkgo. Serotonin syndrome is a serious side effect and may be fatal. Symptoms include fever, muscle stiffness, and changes in mental status such as confusion or hallucinations.



• The risk of neuroleptic malignant syndrome (restlessness, sweating, fever, confusion, and muscle stiffness) may increase with lithium (Eskalith, Lithobid) and tramadol (Ultram).



• Morphine, meperidine (Demerol), and other narcotic pain relievers may cause hypotension and depress the central nervous system and respirations.



• The following drugs may increase the risk of hypertensive crisis when taken with MAOIs or within two weeks of stopping MAOIs:
  
  
  • Decongestants such as pseudoephedrine (Sudafed)
  
  
  
  • Stimulants such as amphetamine, cocaine, methamphetamine, or ephedrine (ma huang, ephedra)
  
  
  
  • cyclobenzaprine (Flexeril)
  
  
  
  • dopamine, methyldopa (Aldomet), or levodopa (Sinemet)
  
  
  
  • epinephrine (EpiPen)
  
  
  
  • methylphenidate (Ritalin) or amphetamine and dextroamphetamine (Adderall
  )
  
  
  • buspirone (Buspar)
     
• MAOIs may increase side effects of the following drugs:
  
  
  • bupropion (Wellbutrin, Wellbutrin SR, Wellbutrin XL, Zyban) - Increases risk of seizures, agitation, and psychotic changes
  
  
  
  • Antidiabetic agents - Increases risk for low blood sugar levels, depression, and seizures
  
  
  
  • mirtazapine (Remeron) - May increase risk for seizures
  
  
  
  • carbamazepine (Tegretol) - May result in high blood pressure, fever, and seizures
     
• Do not eat foods high in tyramine, dopamine, or tryptophan while taking MAOIs or for two weeks after discontinuing MAOIs. Tyramine, dopamine, and tryptophan are chemicals that can interact with MAOIs and cause hypertensive crisis, which is an extremely dangerous side effect. Foods high in these chemicals should be avoided. They include the following:
  
  
  • Dairy products
    
    
    • Cheese, particularly Blue, Camembert, Cheddar, Emmenthaler, Stilton, and Swiss, which contain very high amounts of tyramine
    
    
    
    • Yogurt
       
  • Meat and fish products
    
    
    • Anchovies
    
    
    
    • Beef or chicken liver
    
    
    
    • Other meats or fish that have not been refrigerated, are fermented, or are spoiled
    
    
    
    • Caviar
    
    
    
    • Fermented sausages such as bologna, pepperoni, salami, and summer sausage
    
    
    
    • Game meat
    
    
    
    • Meats prepared with tenderizer
    
    
    
    • Herring
    
    
    
    • Shrimp paste
       
  • Alcoholic beverages
    
    
    • Beer
    
    
    
    • Red wine, especially Chianti
    
    
    
    • Sherry
    
    
    
    • Distilled spirits and liqueurs
       
  • Fruits and vegetables
    
    
    • Fruits such as bananas, raspberries, dried fruits, and overripe fruits (especially avocados and figs)
    
    
    
    • Bean cure, miso soup, sauerkraut, soy sauce, and yeast extracts (such as Marmite)
       
  • Foods containing other chemicals that increase blood pressure
    
    
    • Broad beans (fava beans)
    
    
    
    • Caffeine containing beverages such as coffee, tea, and cola
    
    
    
    • Chocolate
    
    
    
    • Ginseng

• Hypertensive crisis (Hypertensive crisis is the most serious reaction and involves dramatic increases in blood pressure and requires immediate care from the doctor. The hypertensive crisis usually occurs within several hours after ingestion of a drug or food that interacts with MAOIs. Hypertensive crisis can be fatal. Symptoms include severe headache, rapid heart rate, chest pain, neck stiffness, nausea, vomiting, sweating [may include a fever or cold, clammy skin], dilated pupils, and eye sensitivity to light.)



• Manic episodes in persons with bipolar disorder [If not combined with a mood-stabilizing drug, MAOIs may induce manic episodes in individuals with bipolar disorder (manic depression).]



• Increased heart rate or blood pressure in people with hyperthyroid conditions