What is the treatment for levothyroxine (T4) poisoning?

Treatment for Levothyroxine (T4) Poisoning

The treatment for levothyroxine poisoning should focus on gastrointestinal decontamination, supportive care, and beta-blocker therapy to manage symptoms, with more aggressive interventions reserved for severe cases. 1

Initial Management

• Gastrointestinal decontamination:

  • Activated charcoal administration (single dose) for recent ingestions 2
  • Gastric lavage may be considered for very large ingestions if presented early

• Supportive care:

  • Monitor vital signs (heart rate, blood pressure, temperature)
  • Intravenous fluids as needed
  • Oxygen support if respiratory symptoms develop

Pharmacological Management

• Beta-blockers (first-line treatment):

  • Propranolol 60-80 mg orally every 4-6 hours or 1-2 mg IV slowly 3, 4
  • Esmolol can be used as an alternative in cases of hemodynamic instability 3
  • Non-dihydropyridine calcium channel antagonists (diltiazem or verapamil) if beta-blockers are contraindicated 3

• Additional medications (for severe cases):

  • Propylthiouracil to block peripheral conversion of T4 to T3 4, 5
  • Hydrocortisone to reduce peripheral conversion of T4 to T3 5
  • Cholestyramine to interrupt enterohepatic circulation of thyroid hormones

Laboratory Monitoring

• Daily determinations of T3, T4, and TSH levels 4
• Liver function tests (alanine transaminase may be elevated) 6
• Cardiac monitoring for arrhythmias

Severe Cases Management

For severe intoxication with life-threatening symptoms (coma, severe cardiovascular complications):

• Consider plasmapheresis or charcoal hemoperfusion 5
  • Plasmapheresis is more effective for removing T4 (30 times higher elimination rate)
  • Hemoperfusion is more effective for removing T3 5

Clinical Course and Prognosis

• Symptoms may not appear until several days after ingestion 1, 4

• Clinical manifestations include:

  • Cardiovascular: tachycardia, arrhythmias, hypertension
  • Neurological: irritability, tremor, confusion, seizures (rare)
  • Gastrointestinal: vomiting, diarrhea, abdominal pain
  • Metabolic: fever, increased metabolic rate

• Most cases in children have mild symptoms and good outcomes with conservative management 7, 2

• Symptoms can persist for days to weeks, corresponding to the long half-life of levothyroxine

Important Considerations

• The toxic dose is unclear; asymptomatic patients have been observed with doses under 5 mg 4
• Early T3/T4 levels may not correlate with clinical severity 4
• Pediatric cases generally have better outcomes than adults with similar ingestions 7, 2
• Hospitalization is warranted for symptomatic patients or those with very large ingestions
• Contact Poison Control Center (1-800-222-1222) for current management recommendations 1

For most cases of levothyroxine poisoning, especially in children, conservative management with gastrointestinal decontamination and beta-blockers is sufficient, with more aggressive interventions reserved for severe cases with significant clinical manifestations.