Iron poisoning

Iron containing preparations are freely available. Many are brightly coloured, some with a sweet coating. Consequently, iron poisoning is not uncommon in children.

Severe poisoning may result from the ingestion of more than 150 mg/kg. In small children, a dose of 20 mg/kg of elemental iron may cause illness and 600 mg may be fatal to a toddler weighing less than 10 kg (1).

Rapid necrosis of the gastrointestinal mucosa occurs, resulting in haemorrhage and fluid/electrolyte loss. The binding capacity of transferrin is finite, and saturation occurs rapidly as the iron is absorbed; the free serum iron level rises.

• iron overdose causes corrosive damages to gastrointestinal (GI) mucosa and can lead to acute hemorrhagic gastritis, massive fluid loss (because of third spacing), bleeding and shock
  • large amounts of ingested iron overwhelm normal gastrointestinal barriers, resulting in massive iron absorption
    • when serum iron level exceeds the body's binding capacity, free iron produces an increase in reactive oxygen species (ROS) or so called oxygen, free radicals, such as hydroxyl radical, superoxide radical or hydrogen peroxide leading to lipid peroxidation and cellular membrane damage
      • enhanced generation of ROS can overwhelm cells' intrinsic antioxidant defenses and result in "oxidative stress", a term used to describe cellular dysfunction caused by ROS induced damage to lipids, proteins and DNA

Severe poisoning is indicated by serum iron levels above 5 mg/l in a child, or 8 mg/l in an adult. It may be fatal.

Reference:

• CSM/MCA (2001). Current problems in pharmacovigilance, 27, 14.
• Ercal N, Gurer-Orban H, Aykin-Burns N. Toxic metals and oxidative stress part I: Mechanisms involved in metal-induced oxidative damage. Curr Top Med Chem 2001; 1: 529-539.
• Robotham JL, Lietman PS. Acute iron poisoning: A review. Am J Dis Child 1980; 134: 875-879.