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Clinician’s Corner: Monoamine Oxidase Inhibitors (MAOIs)

MAOI (monoamine oxidase inhibitors)

Monoamine Oxidase Inhibitors (MAOIs)  block monoamine oxidase, an enzyme in the synaptic cleft that breaks down neurotransmitters in the brain. MAOIs are very seldom used due to side effects and life-threatening drug interactions:

Hypertensive crisis: extreme increases in blood pressure when MAOIs interact with OTC meds and foods containing tyramine.

      • Tyramine containing foods and OTC drugs that should be avoided:
        • Aged cheeses: blue, camembert, cheddar, Roquefort, stilton and Swiss
        • Anchovies
        • Dried, aged, smoked, fermented, spoiled, or improperly-stored meat, poultry, and fish
        • Tap and non-pasteurized beers
        • Red wine, (esp. Chianti), sherry
        • Many tropical fruits à bananas and avocados (especially if overripe)
        • Also avoid drugs with vasopressors (increase BP): chocolate, cola, coffee tea, broad beans
        • Sauerkraut and soy products (tofu, soy sauce, marmite)
        • OTC cold medications containing pseudoephedrine (Sudafed®)
        • Avoid amphetamines and appetite suppressants
        • Other antidepressants

MAOI Drugs

  • Nardil® (phenelzine) 15mg tablets (FDA approved 1961)
  • Parnate® (tranylcypromine) 10mg tablets (FDA approved 1961)
  • Marplan® (isocarboxazid) 10mg tablets (FDA approved 1959)
  • EMSAM® (selegiline transdermal system) (FDA approved 2006)

Monoamine oxidase inhibitors

SUBSTRATES Norepinephrine  
LOCATION Brain, gut, liver, placenta, skin Brain, platelets, lymphocytes
INHIBITORS Nardil, Parnate Marplan, Emsam Eldepryl (low doses)


THERAPEUTIC USE Depression Parkinson’s disease

Like so many drugs that were discovered in the 1950’s MAOI’s existence is due to serendipity. Researchers discovered that one of the tuberculosis drugs, iproniazid caused relief of patient’s depression.  This led to the discovery of monoamine oxidase, and soon after inhibitors of this enzyme were marketed for the relief of depression.  Due to the side effects and significant food and drug interactions these drugs are seldom used.  About the only time we see this class of drugs used is in treatment resistant depression, that have failed the more common therapies.

Although it has been a long time since I have dispensed these drugs, our local warehouse does have Nardil, Parnate and their generics in stock, along with brand name Emsam.  The selective MAO-B inhibitors used for Parkinson’s disease are a little more commonly dispensed in our pharmacy.

Whether your drugs have been around for decades or whether they were released last year, your Thompson Pharmacist is a great resource for you with all your drug therapies.  Whether mental health, diabetes, cholesterol or blood pressure drugs, we can help you find the best and most cost-effective medicines. Go Ahead and ASK… at Thompson Pharmacy it’s All for YOU!