Monoamine oxidase inhibitor toxicity

Background

• MAOIs are used for depression and Parkinson's (e.g. selegiline)
• Lead to increased norepi, serotonin, dopamine, tyramine
• Toxicity often delayed 6-24hr after ingestion

Clinical Features

• Similar to a hyperadrenergic state
• Severe toxicity is accompanied by:
  • Coma, seizure, bradycardia, hypotension, worsening hyperthermia

DDX

1. Intoxications
   1. Amphetamines, antimuscarinics
2. Withdrawal states
   1. ETOH, clonidine, B-blockers
3. Medical conditions
   1. Heat stroke, hypoglycemia, hyperthyroidism
4. Adverse drug reactions
   1. Malignant Hyperthermia
   2. Serotonin Syndrome
   3. Tyramine Reaction
   4. Neuroleptic Malignant Syndrome (NMS)

Treatment

1. Gastric decontamination
   1. Gastric lavage indicated if can be performed <1hr after ingestion
   2. Activated charcoal x1
2. Supportive care
   1. Hypertension
      1. Treat only with short-acting agents (may develop precipitous hypotension)
      2. Phentolamine
         1. Give 2.5-5mg IV bolus q15-15min; can also give as infusion 0.2-0.5mg/min
      3. Nitroprusside
         1. Give 1mcg/kg/min and titrate up
   2. Hypotension
      1. IVF
      2. Norepi
   3. Seizures
      1. Benzos are 1st line
   4. Hyperthermia
      1. Routine cooling measures
      2. Consider paralysis if pt has persistent muscle rigidity

Disposition

• Admit all pts for 24hr obs

Prevention

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

See Also

• Tyramine Reaction
• Toxidromes

Source

• Tintinalli