What is the toxic dose of iron (Fe) in children?

Toxic Dose of Iron in Children

The toxic dose of iron in children is considered to be ≥40 mg/kg of elemental iron, with doses of 60 mg/kg or higher considered potentially serious and requiring immediate medical evaluation. 1

Understanding Iron Toxicity Thresholds

Iron toxicity in children follows a dose-dependent pattern:

• <20 mg/kg: Generally non-toxic
• 20-40 mg/kg: Mild to moderate toxicity possible
• ≥40 mg/kg: Toxic dose requiring medical evaluation 1
• ≥60 mg/kg: Potentially serious toxicity 1
• >100 mg/kg: Severe, potentially life-threatening toxicity 2

Recent research has suggested that the minimum cut-off dose of elemental iron that triggers serious toxicity requiring chelation therapy may be as low as 28 mg/kg in children under 18 years of age 3.

Clinical Manifestations of Iron Toxicity

Iron toxicity typically presents in stages:

1. Initial phase (0-6 hours): Gastrointestinal symptoms (vomiting, diarrhea, abdominal pain, hematemesis)
2. Latent phase (6-24 hours): Apparent improvement
3. Systemic toxicity phase (24-72 hours): Metabolic acidosis, shock, liver failure, coagulopathy
4. Late complications (2-4 weeks): Gastrointestinal scarring, pyloric stenosis

Assessment and Management

Initial Assessment

• Calculate the amount of elemental iron ingested:
  • Ferrous sulfate: 20% elemental iron
  • Ferrous fumarate: 33% elemental iron
  • Ferrous gluconate: 12% elemental iron

Management Based on Ingested Dose

1. <40 mg/kg with mild symptoms (vomiting, diarrhea):

   • Home observation with appropriate follow-up 1
   • Monitor for worsening symptoms

2. ≥40 mg/kg OR severe/persistent symptoms:

   • Immediate referral to healthcare facility 1
   • Serum iron level within 2-6 hours of ingestion
   • Abdominal X-ray to detect radiopaque tablets

3. Severe toxicity (altered mental status, shock, metabolic acidosis):

   • Aggressive supportive care
   • Chelation therapy with deferoxamine:
     • Initial dose: 15 mg/kg/hr IV (not to exceed this rate for first 1000 mg) 4
     • Subsequent dosing: slower rate, not exceeding 125 mg/hr 4
     • Maximum daily dose: 6000 mg in 24 hours 4

Important Considerations

• Serum iron levels >350-500 μg/dL are associated with significant toxicity
• Symptomatic children have significantly higher median peak serum iron concentrations (66 μmol/L) compared to asymptomatic children (12 μmol/L) 5
• Suspected dose ingested can be a poor predictor of toxicity; clinical symptoms and serum iron levels are more reliable indicators 5

Special Formulations

• Children's chewable vitamins with iron generally pose lower risk and can be observed at home with appropriate follow-up 1
• Carbonyl iron or polysaccharide-iron complex formulations have lower toxicity profiles and can typically be managed with home observation 1

Prevention

• Iron supplements should be stored in child-resistant containers
• Parents should be educated about the potential toxicity of iron supplements
• Iron-containing medications should be kept out of reach of children

Iron poisoning remains a significant concern in pediatric populations despite public health measures reducing exposures in recent decades. Early recognition of toxic ingestions and appropriate management based on ingested dose, clinical symptoms, and laboratory values are essential for preventing serious complications.