Iron toxicity

Background

• Each 325mg ferrous sulfate tablet contains 65mg of elemental iron
• Toxicity
  • Mild: 10-20mg elemental iron/kg
  • Moderate: 20-60mg/kg (approx 20-35 tablets)
  • Severe: >60mg/kg
• Absence of GI symptoms w/in 6hr of ingestion excludes significant iron ingestion

Pathophysiology

• GI tract irritant:
  • N/V, diarrhea, abdominal pain, bleeding
• Electron transport chain disruption:
  • Lactic acidosis
• Portal vein iron delivery to liver:
  • Hepatotoxicity
• Thrombin formation inhibition:
  • Coagulopathy - direct effect on vitamin K clotting factors

Clinical Features

Iron Toxicity Stages

Stage	Clinical Effect	Time Frame
Stage 1	GI irritation: n/v, abd pain, diarrhea	30-60 mins
Stage 2: latent	reduced GI symptoms	6-24 hours
Stage 3: shock and metabolic acidosis	metabolic acidosis, lactic acidosis, dehydration, coags, renal failure	6-72 hours
Stage 4: hepatotox	hepatic failure	12-96 hours
Stage 5: bowel obstruction	GI bowel scarring/healing	2-8 weeks

Work-Up

1. CBC
2. Chemistry
   1. Anion gap metabolic acidosis
   2. Hyperglycemia
3. Coags
4. LFTs
5. Iron levels
6. UA
   1. Used to follow efficacy of Fe chelation (urine changes from rusty color to clear)
7. T&S
8. In ambiguous cases consider abd xray as most Fe tabs are radioopague

Diagnosis

• Serum Iron Concentration
  • Interpret w/ caution: low serum iron levels do not necessarily mean absence of toxicity
  • Levels
    • <300: nontoxic or mild
    • 300-500: Significant GI symptoms and potential for systemic toxicity
    • >500: Moderate to severe systemic toxicity
    • >1000: severe systemic toxicity and increased morbidity

Treatment

1. Asymptomatic pt w/ ingestion of <20mg/kg only requires observation x6hr
2. Volume resuscitation
3. GI decontamination
   1. Consider only for large overdose w/ visible pills in the stomach on x-ray
      1. Whole-bowel irrigation (polyethylene glycol)
         1. Children: 250-500mL/hr
         2. Adults: 2L/hr
      2. Orogastric lavage
   2. Charcoal is not effective
4. Deferoxamine
   1. Indications:
      1. Systemic toxicity
      2. Metabolic acidosis
      3. Progressive symptoms
      4. Serum iron level >500
   2. Dosing:
      1. 1000mg IV; start at 5mg/kg/hr, increase up to 15mg/kg/hr as tolerated
      2. Subsequent doses are 500mg increments guided by clinical status of pt / urine color
      3. Recommended amount during first 24hr is 360mg/kg or 6gm
   3. Side effects:
      1. Hypotension (pre-existing hypotension is NOT a contraindication to therapy)
      2. Contraindicated in renal failure patients not on HD
      3. Long-term use: mucor/yersenia/mucosal infections, renal failure, sepsis
      4. Can see "vin rose" urine
5. Other therapies
   1. Dialysis (removes deferoxamine-iron complex in renal failure pts)
   2. Exchange transfusion

Disposition

• Discharge after 6hr obs for asymptomatic (or only vomited 1-2x) AND ingestion <20mg/kg
• Admit to ICU if deferoxamine required

See Also

Toxidromes

Source

• Tintinalli