Learning objectives

• Describe the side effects and anesthetic consequences of patients on monoamine oxidase inhibitors (MAOI)

Definition and mechanisms

• Monoamine oxidase inhibitors (MAOI) inhibit the activity of one or both monoamine oxidase enzymes A and B, thus preventing the breakdown of monoamine neurotransmitters serotonin and norepinephrine and thereby increasing their availability
  • MAO type A has a preference for norepinephrine and serotonin
  • MAO type B deaminates tyramine and phenylethylamine 
• Risk of hypertensive crisis with norepinephrine release
• MAOIs are effective antidepressants and are used in the treatment of:
  • Panic disorder
  • Atypical depression
  • Anxiety disorder
  • Depression
  • Bulimia
  • Post-traumatic stress disorder
  • Borderline personality disorder
  • Obsessive Compulsive Disorder
  • Bipolar depression
• Be cautious of withdrawal symptoms and recurrence of the psychiatric illness if the psychoactive drug is stopped 
• MAOIs interact severely with commonly used anesthetic agents 
  • MAOIs inhibit the metabolism of indirectly acting sympathomimetics resulting in the potentiation of their action
  • Where necessary, direct sympathomimetics are preferable 

Side effects

• Dry mouth
• Nausea, diarrhea, or constipation
• Headache
• Drowsiness
• Insomnia
• Dizziness or lightheadedness
• Skin reaction at the patch site
• Involuntary muscle jerks
• Low blood pressure
• Reduced sexual desire or difficulty reaching orgasm
• Weight gain
• Difficulty starting a urine flow
• Muscle cramps
• Prickling or tingling sensation in the skin (paresthesia)

Management

Suggested reading

• Peck T, Wong A, Norman E. 2010. Anaesthetic implications of psychoactive drugs. Continuing Education in Anaesthesia Critical Care & Pain.10;(6); 177-181.