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Toxicology / Poisoning

Iron Poisoning

Poisoning resulting from ingestion of excessive amounts of iron salts (commonly ferrous sulphate tablets). Primarily occurs in children due to the candy-like appearance of tablets. Toxicity depends on the dose of elemental iron ingested (<20mg/kg unlikely toxic, 20-60mg/kg mild-moderate, >60mg/kg potentially severe/lethal). Iron is directly corrosive to the GI tract and causes systemic toxicity via cellular dysfunction.

Also known as: Iron Overdose, Ferrous Sulphate Poisoning

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Referral and warning signs

When to refer

ALL children with suspected ingestion >40 mg/kg elemental iron, ALL symptomatic patients (beyond mild transient nausea/vomiting), and ALL patients potentially requiring desferrioxamine MUST be referred urgently to Hospital (H/RR/NR for antidote). Asymptomatic patients with ingestion <40 mg/kg may potentially be observed, but referral is safer if history is uncertain, follow-up unreliable, or any symptoms develop.

Red flags

  • Persistent vomiting or diarrhoea (especially bloody)
  • Signs of shock (hypotension, tachycardia, poor perfusion, altered mental status)
  • Lethargy, confusion, coma
  • Seizures
  • Severe metabolic acidosis
  • Abdominal X-ray showing large number of tablets
  • Serum Iron level > 500 mcg/dL

Signs and symptoms

  • Occur in distinct phases:
  • Phase 1 (0.5 - 6 hours): GI Toxicity - Nausea, vomiting (often forceful, may be bloody/hematemesis), abdominal pain, diarrhoea (often bloody/melena). Can lead to dehydration, hypovolemic shock, metabolic acidosis.
  • Phase 2 (6 - 24 hours): Latent Phase / Apparent Recovery - GI symptoms may temporarily improve or resolve. Patient may seem better, but systemic toxicity is developing.
  • Phase 3 (12 - 48 hours): Systemic Toxicity & Shock - Recurrence/worsening of shock (cardiogenic, hypovolemic, distributive components), severe high anion gap metabolic acidosis, lethargy, confusion, seizures, coma. Hepatotoxicity (liver damage) begins, leading to hypoglycemia, coagulopathy.
  • Phase 4 (2 - 5 days): Hepatic Necrosis / Failure - Jaundice, persistent coagulopathy, hepatic encephalopathy. Acute kidney injury. Acute Respiratory Distress Syndrome (ARDS).
  • Phase 5 (2 - 6 weeks): Late Complication - Gastric outlet obstruction or small bowel strictures due to scarring from initial corrosive injury.

Risk factors

  • Accidental ingestion by young children (most common scenario).
  • Intentional overdose (less common).
  • Ingestion of prenatal vitamins containing high doses of iron.
  • Easy availability of iron tablets (often prescribed for anaemia).

Diagnosis

Clinical assessment

Based on history of ingestion (crucial to determine type of iron salt, number of tablets, and time of ingestion to estimate elemental iron dose in mg/kg). Clinical features corresponding to the phases of toxicity. Assess for severity (shock, altered mental status, acidosis).

Investigations

  • Serum Iron Level: Obtain level 4-6 hours post-ingestion (peak level). Level >350 mcg/dL (63 micromol/L) suggests potential toxicity; >500 mcg/dL (90 micromol/L) associated with severe toxicity. Note: Level correlates poorly with clinical severity later on, and Total Iron Binding Capacity (TIBC) is unreliable in overdose.
  • Abdominal X-ray (AXR): Iron tablets are often radio-opaque. AXR can help confirm ingestion, estimate quantity remaining, and assess for tablet concretions.
  • Blood Glucose: Check frequently for hypoglycemia.
  • Arterial Blood Gas (ABG) / Venous Blood Gas (VBG): Assess for metabolic acidosis (high anion gap) and lactate.
  • Complete Blood Count (CBC): Check WBC (often elevated leukocytosis), Hb/Hct for bleeding.
  • Electrolytes, Renal Function Tests (Urea, Creatinine), Liver Function Tests (AST, ALT, Bili, INR): Monitor for systemic toxicity and organ damage.
  • Rule out co-ingestions.

Diagnostic criteria

History of potentially toxic ingestion (>40-60 mg/kg elemental iron) AND/OR Clinical signs of moderate/severe poisoning (persistent vomiting/diarrhea, shock, acidosis, lethargy/coma) AND/OR Serum iron level > 500 mcg/dL (or >350 mcg/dL with symptoms).

Management

Non-pharmacological management

  • Stabilization: ABCDE approach. Airway management if needed.
  • Fluid Resuscitation: Aggressive IV fluid resuscitation (Normal Saline or Ringer's Lactate) is critical for managing GI losses, hypovolemia, and shock.
  • GI Decontamination:
  • - Gastric Lavage: Generally NOT recommended due to risks and limited efficacy. May consider only for massive, recent (<1 hour) ingestion of life-threatening amount (controversial).
  • - Activated Charcoal: DOES NOT BIND IRON effectively - DO NOT USE.
  • - Whole Bowel Irrigation (WBI): Consider for large ingestions with tablets visible on AXR, presenting early, before significant toxicity develops. Uses polyethylene glycol solution via NGT (Hospital level).
  • Surgical/Endoscopic Removal: Rarely needed for removal of tablet concretions.
  • Supportive Care: Correct acidosis (fluids, sometimes bicarbonate - use cautiously), manage hypoglycemia, treat seizures (benzodiazepines).

Pharmacological treatment

  • ANTIDOTE: Desferrioxamine (Deferoxamine): Iron chelator. Indications: Severe poisoning - Shock, Coma, Seizures, Severe metabolic acidosis, Serum iron level >500 mcg/dL (or >350 mcg/dL with significant symptoms).
  • IV Desferrioxamine: Administer as a continuous IV infusion. Typical starting dose: 15 mg/kg/hour. Titrate based on clinical response and side effects (max rate usually ~35 mg/kg/hr).
  • Monitoring during infusion: Watch closely for hypotension (common side effect - slow infusion rate, increase IV fluids). Pulmonary toxicity (ARDS) reported with high doses/prolonged use.
  • Endpoint: Continue infusion until patient is clinically stable, acidosis resolved, urine colour normalizes (characteristic 'vin rosé' colour indicates iron chelation, but its absence doesn't mandate stopping if clinical indications remain), and serum iron level decreases (ideally <150 mcg/dL). Usually limited to 24 hours if possible, but may require longer based on clinical picture.
  • Contraindications: Severe renal failure / anuria (drug-iron complex excreted renally). Use with caution if renal impairment.
  • IM Desferrioxamine: Less effective, generally not used for severe acute poisoning.

Monitoring

Continuous monitoring of vital signs (especially BP during desferrioxamine infusion). Monitor mental status, GI symptoms, urine output, urine color ('vin rosé'). Serial monitoring of: Serum iron levels, ABG/VBG (for acidosis), Blood glucose, Electrolytes, Renal function, Liver function.

Complications

  • Severe hypovolemic/distributive/cardiogenic shock
  • Severe metabolic acidosis
  • Acute liver failure / Hepatic necrosis
  • Acute kidney injury
  • Coagulopathy
  • ARDS / Pulmonary edema
  • CNS toxicity (lethargy, coma, seizures)
  • GI hemorrhage / perforation
  • Late GI scarring causing gastric outlet obstruction or bowel strictures
  • Yersinia sepsis (rare - iron enhances bacterial growth)
  • Death

Prevention

  • Keep all medications, especially iron tablets and prenatal vitamins, securely stored out of sight and reach of children.
  • Use child-resistant packaging.
  • Educate parents and caregivers about the danger of iron poisoning.
  • Prescribe/dispense only necessary quantities.
  • Consider lower-risk iron formulations where appropriate.

Patient education

  • Explain the serious danger of iron tablets to children.
  • Reinforce the critical importance of safe storage.
  • Advise seeking immediate medical evaluation after any suspected ingestion.
  • If chelation therapy given, explain rationale and monitoring needed.

Uganda-specific notes

Iron tablets (ferrous sulphate) are very commonly prescribed for anaemia, increasing risk of accidental ingestion. Crucial to calculate elemental iron dose accurately (e.g., standard 200mg ferrous sulphate tablet contains ~60-65mg elemental iron). Desferrioxamine (antidote) availability is likely limited or non-existent in many settings (NR). Management heavily relies on aggressive supportive care (especially IV fluids) and monitoring. Remember Activated Charcoal is NOT effective. Abdominal X-ray can be very helpful if available.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 1, Section 1.3.6

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