Monoamine Oxidase (MAO) Inhibitors

Psychiatric Drug Introduction

• Psychiatric medications can be broken down into the following categores
  • antidepressants
  • antipsychotics
  • bipolar medications
• anxiolytics

Overview

• Drugs
  • non-selective inhibitors
    • phenelzine
    • tranylcypromine
    • isocarboxazid
  • MAO-B selective inhibitor
    • selegiline
      • used in Parkinson’s treatment to increase dopamine levels
• Mechanism
  • ↓ MAO → ↓ amine degradation → ↑ levels of amine neurotransmitters (mainly NE, 5-HT)
• Clinical use
  • atypical depression
  • anxiety
  • hypochondriasis
• Toxicity
  • hypertensive crisis caused by 
    • tyramine ingestion  
      • tyramine found in many foods, such as wine and cheese
      • MAO normally degrades Norepinephrine (NE) (increased release of catecholamines with tyramine ingestion), when MAOIs taken with Tyramine, increase in NE results in sympathetic activation of vascular tone through alpha adrenergic receptors resulting in hypertension.
    • other sympathomimetics
  • CNS stimulation
  • contraindicated with other 5-HT altering drugs (SSRIs, SNRIs) or meperidine
    • to prevent serotonin syndrome