Iron poisoning

Iron poisoning is an iron overload caused by a large excess of iron intake and usually refers to an acute overload rather than a gradual one. The term has been primarily associated with young children[1] who consumed large quantities of iron supplement pills, which resemble sweets and are widely used, including by pregnant women; approximately 3 grams is lethal for a two-year-old.[2] Targeted packaging restrictions in the US for supplement containers with over 250 mg elemental iron have existed since 1978, and recommendations for unit packaging have reduced the several iron poisoning fatalities per year to almost zero since 1998.[3][4] No known cases of iron poisoning have been identified that are associated with iron mining.

Iron poisoning
Other namesiron toxicity, iron overdose

Signs and symptoms

The first indication of iron poisoning by ingestion is stomach pain, as iron is corrosive to the lining of the gastrointestinal tract, including the stomach. Nausea and vomiting are also common symptoms and bloody vomiting may occur. The pain then abates for 24 hours as the iron passes deeper into the body, resulting in metabolic acidosis, which in turn damages internal organs, particularly the brain and the liver. Iron poisoning can cause hypovolemic shock due to iron's potent ability to dilate the blood vessels. Death may occur from liver failure.

If intake of iron is for a prolonged period of time, symptoms are likely to be similar to other causes of iron overload.

Cause

In nature, iron is usually found in its oxidized form, iron (III) oxide, which is insoluble. Ferrous iron, iron (II), is soluble and its toxicity varies, largely with the integrity of the gastrointestinal lining. Iron supplements are typically used to treat anemia. Modalities include: diet, parasite control,[5] vitamin A, riboflavin (B2),[6] vitamin C (for absorption), folate(B9), vitamin B12 and multivitamin-multimineral supplements,[7] with or without iron; potentially avoiding the use of iron only supplements.[8]

Toxic dose

The amount of iron ingested may give a clue to potential toxicity. The therapeutic dose for iron deficiency anemia is 3–6 mg/kg/day. Toxic effects begin to occur at doses above 10–20 mg/kg of elemental iron. Ingestions of more than 50 mg/kg of elemental iron are associated with severe toxicity.[9]

  • A 325-mg tablet of ferrous sulfate heptahydrate has 65 mg (20%) of elemental iron
  • A 325-mg tablet of ferrous gluconate has 39 mg (12%) of elemental iron
  • A 325-mg tablet of ferrous fumarate has 107.25 mg (33%) of elemental iron
  • 200 mg ferrous sulfate, dried, has 65 mg (33%) of elemental iron

In terms of blood values, iron levels above 350–500 μg/dL are considered toxic, and levels over 1000 μg/dL indicate severe iron poisoning.[10]

Diagnosis

A detailed history of the ingestion, especially the number of pills taken, can be vital. Diagnosis of iron poisoning can be made in the absence of a specific history by clinical judgment, imagining investigation and lab assessment. Iron tablets may be imaged by radiography. Serum iron levels can be tested and are useful regarding the administration of iron-binding ligands such as deferoxamine. Clinic presentation in the absence of treatment follows in stages and is dose dependent (how much iron was taken):[11][12]

Stage Time Post Ingestion Signs Symptoms
1 1–6 hours Vomiting, diarrhea, GI bleeding, circulatory shock from hemorrhage and vasodilation Abdominal pain
2 6–12 hours Possible resolution of some signs based on treatment and dosage of poisoning Resolution of symptoms (considered a dangerous period if severe poisoning but if mild then may indicate a true turning point)
3 12–36 hours Metabolic acidosis, circulatory collapse, hepatic failure

Renal failure

D.I.C.

Neurologic decline
4 2–6 weeks Signs of fibrosis at the pyloric region and elsewhere in the intestine with concomitant stenosis (narrowing)

Treatment

Later stage treatment consists of cleaning the iron from the blood, using a chelating agent such as deferoxamine. If this fails then dialysis is the next step.

See also

Footnotes and references
  1. Valentine, Kevin; Mastropietro, Christopher; Sarnaik, Ashok P. "Infantile iron poisoning: Challenges in diagnosis and management". Pediatric Critical Care Medicine. 10 (3): e31–e33. doi:10.1097/pcc.0b013e318198b0c2.
  2. "Iron Toxicity, What You Don't Know". Plants Poisonous to Livestock. Cornell University Department of Animal Science. Retrieved 2012-04-09.
  3. Tenenbein, M. (June 2005). "Unit-Dose Packaging of Iron Supplements and Reduction of Iron Poisoning in Young Children". Arch Pediatr Adolesc Med. 159: 557–560. doi:10.1001/archpedi.159.6.557. PMID 15939855.
  4. "AAPCC Annual Reports". American Association of Poison Control Centers. Archived from the original on 2008-05-22.
  5. Stoltzfus RJ, Dreyfuss ML (2000). "Guidelines for the Use of Iron Supplements to Prevent and Treat Iron Deficiency Anemia" (PDF). International Nutritional Anemia Consultative Group, International Life Sciences Institute Press.
  6. Allen LH (April 2002). "Iron Supplements: Scientific Issues Concerning Efficacy and Implications for Research and Programs". J. Nutr. 132 (4): 813S–9S. PMID 11925487.
  7. "What Is Anemia?". National Heart, Lung, and Blood Institute, U.S. Dept. of Health and Human Services. 18 May 2012.
  8. "Hemochromatosis and Anemia Diet". Iron Overload Diseases Association.
  9. "Iron Poisoning". Webmd.com. Retrieved 2012-04-09.
  10. "Iron Tests". The Free Dictionary by Falex. citing: Gale Encyclopedia of Medicine. Copyright 2008
  11. Pediatrics. Brown, Lloyd J., Miller, Lee T. (Lee Todd). Philadelphia: Lippincott Williams & Wilkins. 2005. ISBN 9780781721295. OCLC 54913574.CS1 maint: others (link)
  12. "Approach to the child with occult toxic exposure". www.uptodate.com. Retrieved 2018-01-04.
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