MAOI toxicity - NYSORA

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MAOI toxicity

Learning objectives

  • Diagnose and treat MAOI toxicity

Definition and mechanisms

  • Monoamine oxidase inhibitors (MAOIs) are a class of antidepressants
  • MAOIs prevent the breakdown of monoamine neurotransmitters serotonin and norepinephrine and thereby increasing their availability
  • MAOIs interact severely with commonly used anesthetic agents 
  • MAOI toxicity can be difficult to distinguish from much more common clinical entities
  • Without MAO to break down epinephrine, norepinephrine, dopamine, serotonin, and tyramine, the storage, and release of these monoamines are increased
  • In this way leading to tachycardia, hyperthermia, myoclonus, hypertension, and agitation
  • Plasma concentrations peak within two to three hours
  • Three ways in which MAOI toxicity can occur:
    • Drug-food interaction with tyramine-containing foods
      • When MAO found in the gut and liver is inhibited, dietary tyramine indirectly causes an amplification of adrenergic activity
      • Aged cheeses, beer wine, ginseng, avocado
    • Overdose as MAOIs have a low therapeutic index
    • Drug-drug interaction when a MAOI is combined with other agents that increases the synthesis, release, and effect or decreases the metabolism or reuptake of monoamines
      • Dextromethorphan, linezolid, methylene blue, selective serotonin reuptake inhibitors, serotoninergic agents, and tramadol

Signs and symptoms

Mild signsAgitation
Diaphoresis
Tachycardia
Mild temperature elevation
Moderate signsAltered mental status
Tachypnea
Vomiting
Dysrhythmias
Hypertension
Severe signsSevere hyperthermia
Seizures
Central nervous system (CNS) depression
Coma
Cardiorespiratory depression
Muscle rigidity
Myoclonus
  • MAOI toxicity can present with diaphoresis whereas an anticholinergic syndrome should have dry skin
  • MAOI toxicity is much more likely to present with generalized or ocular clonus than neuroleptic malignant syndrome

Diagnosis

  • History and physical examination
  • Frequent temperature measurements
  • Electrolytes and lactic acid
  • Salicylate, acetaminophen, and alcohol levels should be obtained

Management

MAOI toxicity, serotonin syndrome, moclobemide, phenelzine, tranylcypromine, activated charcoal, cyproheptadine, olanzapine, evaporative cooling, ice packs, ice bath, benzodiazepines, nitroprusside, phentolamine

Anesthetic management

Suggested reading

  • Bartakke, A., Corredor, C., Van Rensburg, A., 2020. Serotonin syndrome in the perioperative period. BJA Education 20, 10–17.
  • Peck T, Wong A, Norman E. 2010. Anaesthetic implications of psychoactive drugs. Continuing Education in Anaesthesia Critical Care & Pain.10;(6); 177-181.
  • Gillman, P.K., 2005. Monoamine oxidase inhibitors, opioid analgesics and serotonin toxicity. British Journal of Anaesthesia 95, 434–441.

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