What is the lethal dose of iron (Fe) poisoning in pediatric and adult patients?

Iron Poisoning Lethal Dose

Acute iron ingestion exceeding 60 mg/kg of elemental iron is potentially life-threatening, with documented survival reported even at extraordinarily high serum iron levels of 16,706 mcg/dL (2992 µmol/L), though mortality risk increases substantially above this threshold. 1, 2

Dose Thresholds for Toxicity

Pediatric and Adult Acute Ingestion

• Ingestions of ≥40 mg/kg elemental iron require immediate referral to a healthcare facility for medical evaluation, as this represents the threshold for potentially serious toxicity 3
• Ingestions of ≥60 mg/kg elemental iron are considered potentially serious and life-threatening, requiring aggressive management including chelation therapy with deferoxamine 1
• Ingestions <40 mg/kg with only mild symptoms (simple vomiting, diarrhea) can be observed at home with appropriate follow-up 3

Documented Survival Cases

• A case report documented survival after ingestion of 390 mg/kg elemental iron (approximately 50 ferrous sulfate tablets in an 11-month-old), with initial serum iron of 14,250 mcg/dL, treated with aggressive deferoxamine therapy, gastric decontamination, and supportive care 1
• Another case reported survival after 16,706 mcg/dL serum iron level (approximately 50 tablets, 60 mg elemental iron each, in a 22-month-old), representing the highest documented survival with iron poisoning, treated with intermittent high-dose deferoxamine (25 mg/kg/h for 12 hours daily × 3 days) 2
• A recent case demonstrated benign outcome after 88 mg/kg elemental iron ingestion in an adult with minimal symptoms managed with supportive care alone 4

Clinical Severity Assessment

Symptoms Requiring Immediate Referral

• Persistent or severe vomiting and diarrhea (beyond mild transient symptoms) 3
• Alterations in level of consciousness or coma 1, 2
• Hematemesis or bloody diarrhea 3
• Shock (hypovolemic or cardiogenic) 2
• Metabolic acidosis with elevated anion gap 5, 2

Laboratory Indicators of Severe Toxicity

• Serum iron >500 mcg/dL measured 4-6 hours post-ingestion indicates significant toxicity requiring chelation 4
• Serum iron >1000 mcg/dL represents severe poisoning with high mortality risk without aggressive treatment 5, 1
• Initial hyperglycemia and leukocytosis may indicate severe toxicity 1

Chronic Therapeutic Iron Toxicity (Iatrogenic)

Intravenous Iron in Dialysis Patients

• Cumulative IV iron doses >820 mg per 6 months (>136 mg/month) significantly increase mortality (HR 3.1-3.7) and cardiovascular events (HR 3.5-5.1) in hemodialysis patients 6
• Monthly IV iron doses ≥300-400 mg increase adjusted mortality (HR 1.13-1.18) and hospitalization risk in long-term follow-up studies 6
• High-dose IV iron (>200 mg/month) dramatically increases acute cardiocerebrovascular disease risk (HR 6.02) and infections (HR 5.22) 6

Pediatric Parenteral Nutrition

• Systemic iron toxicity with hepatocellular damage occurred in a pediatric patient receiving 16 mg/kg of iron sucrose, demonstrating toxicity at this dose level in the parenteral setting 6
• Recommended maximum single dose is 300 mg for intermittent IV iron infusions in children 6

Critical Management Principles

When to Initiate Chelation Therapy

• Begin deferoxamine for ingestions >60 mg/kg with symptoms or serum iron >500 mcg/dL 1, 3
• Deferoxamine dosing: continuous IV infusion at 15 mg/kg/h is standard, though higher doses (25 mg/kg/h for 12 hours daily) have been used successfully in massive overdoses 2
• Continue chelation until serum iron normalizes and clinical improvement occurs, typically 24-48 hours 5, 1

Gastrointestinal Decontamination

• Gastric lavage with deferoxamine-containing solution may be beneficial in severe cases presenting within hours of ingestion 1
• Whole-bowel irrigation with polyethylene glycol-electrolyte solution is indicated when radiographs show retained iron tablets 1
• Do NOT use ipecac, activated charcoal, cathartics, or oral complexing agents (bicarbonate, phosphate) in out-of-hospital management 3

Adjunctive Therapies for Severe Cases

• Hemodialysis may assist in decreasing serum iron concentration in massive overdoses with life-threatening toxicity (e.g., serum iron >2000 mcg/dL) 5
• Supportive care including volume resuscitation, blood products for coagulopathy, and hemodynamic monitoring with Swan-Ganz catheter in shock states 2

Important Clinical Pitfalls

Timing Considerations

• Asymptomatic patients >6 hours post-ingestion are unlikely to develop delayed symptoms and generally do not require referral or prolonged observation 3
• Serum iron levels must be measured 4-6 hours post-ingestion for accurate assessment of toxicity, as earlier levels may not reflect peak absorption 4

Special Populations

• Children's chewable vitamins with iron rarely cause serious toxicity and can be managed with home observation; diarrhea is often due to sorbitol content rather than iron toxicity 3
• Carbonyl iron and polysaccharide-iron complex formulations are less toxic than ferrous salt formulations and typically require only home observation 3
• Pregnant women should use pre-pregnancy weight when calculating mg/kg dose, with the same 40 mg/kg threshold for referral 3

Multi-Organ Complications

• Iron toxicity affects gastrointestinal tract (necrotizing gastroenteritis), cardiovascular system (shock, cardiac failure), liver (hepatic failure, coagulopathy), metabolic system (severe acidosis), and central nervous system (coma) 1, 2
• Adult respiratory distress syndrome can be caused by both iron toxicity and deferoxamine therapy itself, requiring careful monitoring 2