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Iron poisoning is the leading cause of poisoning deaths in children. Symptoms begin with acute gastroenteritis, followed by a quiescent period, then shock and hepatic failure. Diagnosis is by measuring serum iron, detecting radiopaque iron tablets in the GI tract, or detecting unexplained metabolic acidosis in patients with other findings suggesting iron poisoning. Treatment of a substantial ingestion is usually whole-bowel irrigation and chelation therapy with IV deferoxamine.

Many commonly used OTC preparations contain iron. Of the many iron compounds used in OTC and prescription preparations, the most common are ferrous sulfate Some Trade Names
FEOSOL
FER-GEN-SOL
FER-IN-SOL
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(20% elemental iron), ferrous gluconate Some Trade Names
FERGON
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(12% elemental iron), and ferrous fumarate Some Trade Names
FEMIRON
FERRO-SEQUELS
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(33% elemental iron). To children, iron tablets may look like candy. Prenatal multivitamins are the source of iron in most lethal ingestions among children. Children's chewable multivitamins with iron usually have such small amounts that toxicity rarely occurs.

Iron is toxic to the GI, cardiovascular, and central nervous systems. Specific mechanisms are unclear, but excess free iron is inserted into enzymatic processes and interferes with oxidative phosphorylation, producing metabolic acidosis. Iron also catalyzes free radical formation, acts as an oxidizer, and, when plasma protein binding is saturated, combines with water to form iron hydroxide and free H⁺ ions, compounding the metabolic acidosis. Coagulopathy may appear early because of interference with the coagulation cascade and later because of liver injury. Up to 20 mg/kg of elemental iron is not toxic; 20 to 60 mg/kg is mildly to moderately toxic, and > 60 mg/kg can cause severe symptoms and morbidity.

Symptoms, Signs, and Diagnosis

Symptoms occur in 5 stages (see Table 7: Poisoning: Stages of Iron Poisoning); however, symptoms and their progression vary significantly. The severity of stage 1 symptoms usually reflects the overall severity of poisoning; late-stage symptoms develop only if stage 1 symptoms are moderate or severe.

Table 7
Stages of Iron Poisoning Stage Time Postingestion Description 1 Within 6 h Vomiting, hematemesis, explosive diarrhea, irritability, abdominal pain, and lethargy If toxicity is severe, tachypnea, tachycardia, hypotension, coma, and metabolic acidosis 2 Within 6–48 h Up to 24 h of apparent improvement (latent period) 3 12–48 h Shock, seizures, fever, coagulopathy, and metabolic acidosis 4 2–5 days Hepatic failure, jaundice, coagulopathy, and hypoglycemia 5 2–5 wk Gastric outlet or duodenal obstruction secondary to scarring

Iron poisoning should be considered in mixed ingestions (because iron is ubiquitous) and in small children with access to iron and unexplained metabolic acidosis or severe or hemorrhagic gastroenteritis. Because children often share, siblings and playmates of small children who have ingested iron should be evaluated.

Abdominal x-ray is usually recommended to confirm ingestion; it detects intact iron tablets or iron concretions but misses chewed and dissolved tablets, liquid iron preparations, and iron in multivitamin preparations. Serum iron, electrolytes, and pH are determined 3 to 4 h after ingestion. Toxicity is assumed if suspected ingestion is accompanied by vomiting and abdominal pain, serum iron levels > 350 μg/dL (63 μmol/L), iron visible on x-ray, or unexplained metabolic acidosis. These iron levels may indicate toxicity; however, iron levels alone do not predict toxicity accurately. Total iron binding capacity (TIBC) is often inaccurate and not helpful in diagnosing serious poisoning and is not recommended. The most accurate approach is to serially measure levels of serum iron, HCO₃, and pH (with calculation of the anion gap); these findings are then evaluated together, and results are correlated with the patient's clinical status. For example, toxicity is suggested by increasing iron levels, metabolic acidosis, worsening symptoms, or, more typically, some combination of these findings.

Prognosis and Treatment

If no symptoms develop within the 1st 6 h after ingestion, risk of serious toxicity is minimal. If shock and coma develop within the 1st 6 h, the mortality rate is about 10%.

If radiopaque tablets are visible on abdominal x-ray, whole-bowel irrigation with polyethylene glycol 1 to 2 L/h for adults or 24 to 40 mL/kg/h for children is done until no iron is visible on repeat abdominal x-ray. Gastric lavage is usually not helpful because vomiting tends to empty the stomach more efficiently. Activated charcoal does not adsorb iron and should be used only if other toxins were also ingested.

All patients with more than mild gastroenteritis are hospitalized. Patients with severe toxicity (metabolic acidosis, shock, severe gastroenteritis, or serum iron level > 500 μg/dL) are treated with IV deferoxamine Some Trade Names
DESFERAL
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to chelate free serum iron. Deferoxamine Some Trade Names
DESFERAL
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is infused at rates up to 15 mg/kg/h IV, titrated until hypotension occurs. Because both deferoxamine Some Trade Names
DESFERAL
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and iron poisoning can decrease BP, patients receiving deferoxamine Some Trade Names
DESFERAL
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require IV hydration.

Last full review/revision November 2005

Content last modified November 2005