Write FMGE oriented short notes on Iron poisoning.
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Iron Poisoning - FMGE Short Notes
Introduction
Iron is an essential mineral for hemoglobin synthesis and metabolic activity. When present in excess (as in overdose), free/unbound iron circulates and causes systemic toxicity. Iron poisoning was historically the leading cause of poisoning death in children.
Sources / Preparations
Common iron preparations and their elemental iron content:
| Compound | % Elemental Iron |
|---|---|
| Ferrous fumarate | 33% |
| Ferrous sulfate | 20% |
| Ferrous gluconate | 12% |
| Ferric chloride | Toxic salt |
- Carbonyl iron and iron polysaccharide are non-ionic newer forms - lower toxicity, no reported deaths.
Mechanism of Toxicity
Iron exerts two distinct toxic effects:
- Direct caustic injury to gastrointestinal (GI) mucosa - causes hemorrhagic necrosis, perforation, and peritonitis.
- Impaired cellular metabolism - primarily heart, liver, and CNS.
Specific mechanisms:
- Uncoupling of oxidative phosphorylation - iron localizes near mitochondrial cristae, impairs ATP synthesis.
- Metabolic acidosis - hydration of the iron molecule releases excess unbuffered protons; free radical-mediated lipid peroxidation injures cell membranes.
- Cardiovascular toxicity - increased capillary permeability, arteriolar and venodilation, direct myocardial depression - leading to shock and cardiovascular collapse.
- Hepatotoxicity - iron deposits in hepatocytes causing centrilobular necrosis.
Chemical test: Ammonium sulfide + ferric/ferrous salts = black precipitate, soluble in dilute HCl.
Toxic Doses (High-yield for FMGE)
| Elemental Iron Ingested | Outcome |
|---|---|
| < 20 mg/kg | Usually no symptoms |
| 20-60 mg/kg | Mild to moderate toxicity |
| > 60 mg/kg | Severe morbidity and mortality |
| Fatal dose | 20-30 g (approx.) |
Clinical Stages (Most Important for FMGE)
4-Stage Classification (Forensic/Indian Textbooks)
| Stage | Time | Features |
|---|---|---|
| Stage I | 0-6 hours | Vomiting, abdominal pain, hemorrhagic gastroenteritis, shock, acidosis, coma |
| Stage II | 6-24 hours | Latent/symptom-free phase (apparent recovery - DO NOT be falsely reassured) |
| Stage III | 24-48 hours | Metabolic acidosis, jaundice, hypoglycemia, shock, coma, hepatic and renal failure |
| Stage IV | 1-2 weeks | Late complications: gastric stricture, pyloric stenosis |
5-Stage Classification (Rosen's Emergency Medicine)
| Stage | Time | Features |
|---|---|---|
| Stage 1 | 0-6 hours | GI toxicity - N/V, diarrhea, abdominal pain, hemorrhagic gastroenteritis |
| Stage 2 | 6-24 hours | Latent phase - apparent improvement |
| Stage 3 | 6-72 hours | Systemic toxicity - metabolic acidosis, shock, hepatotoxicity, coagulopathy, CNS depression |
| Stage 4 | 2-5 days | Hepatic failure - peak hepatotoxicity; fatality most common in this phase |
| Stage 5 | 2-8 weeks | GI stricture/obstruction - pyloric stenosis, scarring from initial mucosal injury |
FMGE tip: Stage II (latent/symptom-free phase) and Stage IV/V (pyloric stenosis as late complication) are classic MCQ traps.
Diagnosis
- Serum iron level (at 3-6 hours post-ingestion) - most useful test.
- < 350 µg/dL: Minimal toxicity
- 350-500 µg/dL: Moderate toxicity
- > 500 µg/dL: Severe toxicity - indicates need for chelation
- TIBC (Total Iron Binding Capacity): NOT a reliable test to gauge severity.
- ABG: Metabolic acidosis (high anion gap).
- Abdominal X-ray: Can visualize radio-opaque iron tablets in the GI tract - confirms ingestion.
- Liver function tests, serum glucose, coagulation profile.
- Urine: On deferoxamine challenge - urine turns "vin rose" (pink/rose) color = positive for iron overload (deferoxamine test).
Treatment
1. GI Decontamination
- Whole Bowel Irrigation (WBI) with polyethylene glycol - method of choice, especially if tablets visible on X-ray.
- Gastric lavage with 1% sodium bicarbonate or 5-15% disodium phosphate solution (to form insoluble iron phosphate).
- Activated charcoal is NOT effective for iron.
2. Antidote - Deferoxamine (Desferrioxamine) ★★★
- Drug of choice / specific antidote for iron poisoning.
- 1 g of deferoxamine chelates 85 mg of elemental iron.
- Forms ferrioxamine - a water-soluble, renally excreted complex.
- Urine turns "vin rose" (pink) color when deferoxamine binds iron - indicates significant iron overload.
Indications for deferoxamine:
- Serum iron > 500 µg/dL
- Severe symptoms regardless of iron level
- Metabolic acidosis, hypotension, altered consciousness
Dosing:
- Intragastric: 5 g dissolved in 100 mL distilled water via stomach tube (left in situ).
- IM: 1 g in 5 mL distilled water; then 500 mg at 12-24 hours.
- IV: Max 15 mg/kg/hour (max 60-80 mg/kg/24 hours) - preferred route for severe poisoning.
- SC route (via portable infusion device) - NOT recommended in acute iron poisoning.
3. Supportive Treatment
- Treat shock - IV fluids, vasopressors.
- Correct metabolic acidosis.
- Manage hepatic failure as needed.
- Cathartics (if no bowel perforation).
Autopsy Findings
- GI tract: Congestion, inflammation, and corrosion of mucosa.
- Liver: Hepatic necrotic (centrilobular) changes.
- Kidney: Renal tubular necrosis.
Medicolegal Aspects
- Most common scenario: Accidental poisoning in children (mistake iron tablets for sweets/candy).
- Ferric chloride: Rarely used for homicidal purposes.
- Iron solutions used locally in genital tract to procure abortion.
- Suicide cases are rare.
High-Yield FMGE One-Liners
| Question Pattern | Answer |
|---|---|
| Specific antidote for iron poisoning | Deferoxamine |
| 1 g deferoxamine chelates how much iron? | 85 mg |
| Urine color after deferoxamine in iron poisoning | Vin rose (pink) |
| Symptom-free (latent) phase in iron poisoning | Stage II (6-24 hours) |
| Late complication of iron poisoning | Pyloric stenosis / gastric stricture |
| Most useful lab test | Serum iron at 3-6 hours |
| Fatal dose of iron | 20-30 g |
| Severe toxicity threshold (serum iron) | > 500 µg/dL |
| GI decontamination of choice | Whole bowel irrigation |
| Activated charcoal useful in iron poisoning? | No |
| Mechanism of metabolic acidosis | Uncoupling of oxidative phosphorylation + free proton release |
| Chemical test for iron | Ammonium sulfide → black precipitate (soluble in dil. HCl) |
Sources: The Essentials of Forensic Medicine and Toxicology 36th ed. (2026); PC Dikshit Textbook of Forensic Medicine and Toxicology; Rosen's Emergency Medicine 9th ed.
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