Monoamine oxidase inhibitor toxicity


  • MonoAmine Oxidase Inhibitors (MAOI)
  • Used to treat depression and Parkinsonism (e.g. selegiline)
  • Lead to increased norepinephrine, serotonin, dopamine, tyramine

Toxicity Mechanisms

  • Intentional overdose
    • Symptoms often delayed 6-24 hours after ingestion
  • Food-drug interactions
    • Taking MAOI at therapeutic doses, but inadvertently eating foods rich in tyramine (aged cheese, red wine)
    • Symptoms are generally acute
  • Drug-drug interactions
    • Many prescription and OTC medications interact with MAOI


  • MAO-A
    • Primarily deaminates serotonin and norepinephrine
  • MOA-B
    • Primarily deaminates phenylethylamine

Clinical Features

Differential Diagnosis


  • asymptomatic period followed by delayed toxicity can suggest MAO-I toxicity
  • urine immunoassays and mass spectroscopy can fail to detect MAOI
  • consider ECG and chemistry panel in MAOI overdose patients who are obtunded


  1. Gastric decontamination
  2. Supportive care
    • Hypertension
      • Treat only with short-acting agents: may develop precipitous hypotension
      • Phentolamine: 2.5-5mg IV bolus q15-15min; can also give as infusion 0.2-0.5mg/min
      • Nitroprusside: 1mcg/kg/min and titrate up
    • Hypotension: intravenous fluid +/- norepinephrine
    • Seizures: benzodiazepines are 1st line
    • Hyperthermia
      • Routine cooling measures
      • Consider paralysis if patient has persistent muscle rigidity


  • Admit all patients for 24 hour observation to monitored setting


  • Do not prescribe the following medications if a patient is taking a MAOI: meperidine, dextromethorphan, tramadol, propoxyphene, or cyclobenzaprine

See Also


  • Rosen's


Ross Donaldson