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Monoamine Oxidase Inhibitor Poisoning

Monoamine Oxidase Inhibitor Poisoning is a topic covered in the 5-Minute Emergency Consult.

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  • Primarily for depression
  • Selegiline, a selective monoamine oxidase B inhibitor, is sometimes used to treat Parkinson disease, and also comes in a transdermal preparation.
  • Monoamine oxidase inhibitor (MAOI) pharmacologic actions:
    • Disruption of equilibrium between endogenous monoamine synthesis and degradation, resulting in:
      • Increased neural norepinephrine levels
      • Downregulation of several receptor types
    • Inhibition of irreversible (noncompetitive) enzyme
    • Inhibition of other B6-containing enzymes
  • MAO: Principal inactivator of neural bioactive amines:
    • MAO A:
      • Present in the gut and liver
      • Protects against dietary bioactive amines
    • MAO B:
      • Present in neuron terminals and platelets
      • Sympathomimetic amines: Types of bioactive amines


  • MAOI overdose:
    • Toxicopharmacology poorly understood
    • MAO inhibitors: Amphetamine-like in structure:
      • Early: Indirect sympathomimetic effect
      • Late: Sympatholytic response (hypotension)
  • MAOI hypertensive crisis syndrome:
    • Results from impaired norepinephrine degradation and large norepinephrine release precipitated by an indirect- or mixed-acting sympathomimetic agent
    • Common precipitants: Tyramine, cocaine, amphetamines
  • Serotonin syndrome (SS):
    • Commonly results from exposure to combinations of agents that affect serotonin metabolism or action
    • Increases serotonin synthesis: Tryptophan
    • Increase serotonin release:
      • Indirect- and mixed-acting sympathomimetic agents and dopamine receptor agonists
    • Decrease serotonin reuptake:
      • Selective serotonin reuptake inhibitors
      • Tricyclic antidepressants
      • Newer antidepressants: Trazodone, nefazodone, venlafaxine
      • Phenylpiperidine opioids: Meperidine, dextromethorphan, tramadol, methadone, propoxyphene
    • Direct serotonin receptor agonists:
      • Buspirone, sumatriptan, lysergic acid diethylamide
    • Decrease serotonin breakdown:
      • MAOIs
    • Increases nonspecific serotonin activity:
      • Lithium

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Rosen, Peter, et al., editors. "Monoamine Oxidase Inhibitor Poisoning." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307212/all/Monoamine_Oxidase_Inhibitor_Poisoning.
Monoamine Oxidase Inhibitor Poisoning. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307212/all/Monoamine_Oxidase_Inhibitor_Poisoning. Accessed April 22, 2019.
Monoamine Oxidase Inhibitor Poisoning. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307212/all/Monoamine_Oxidase_Inhibitor_Poisoning
Monoamine Oxidase Inhibitor Poisoning [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 22]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307212/all/Monoamine_Oxidase_Inhibitor_Poisoning.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Monoamine Oxidase Inhibitor Poisoning ID - 307212 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307212/all/Monoamine_Oxidase_Inhibitor_Poisoning PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -