Chapter 192

Iron supplements are widely available, particularly in homes with small children and young women. Children make up the majority of those with potentially toxic iron exposures, because they may be attracted to the bright color and sugar coating of the tablets, iron tablets left over from pregnancy may be present in homes with toddlers, and iron may not be considered a poison and thus may be stored unsafely.1–3 Fortunately, most children remain asymptomatic or develop only minimal toxicity following exposure. Women of childbearing age are at particular risk for intentional iron overdose due to the availability of iron and increased stress during pregnancy and the postnatal period.4 Iatrogenic iron overdose is rare.5 Unusual circumstances associated with pediatric iron poisoning include accidental administration of ferrous sulfate to an infant and purposeful administration of iron as a means of child abuse.6,7 Those with large overdoses, or adults with intentional overdose, are at risk of toxicity or death without aggressive supportive and antidotal therapy.

In 1997, the U.S. Food and Drug Administration issued a regulation for unit-dose packaging of iron supplements. Analysis of reports of iron ingestion to U.S. poison control centers for the 5 years after the issuance of this regulation showed a significant decrease in calls and reported deaths associated with iron exposure.8 Thus, although in 2008 the American Association of Poison Control Centers’ National Poison Data System received reports of >25,000 exposures to iron, the majority were to vitamin preparations containing iron, and for the >4000 exposures to iron supplements, there were no reported deaths.1

The total-body iron store averages about 4 grams in adults; the range is between 2 and 6 grams, with less iron in women than in men. About two thirds of body iron is incorporated into hemoglobin and the remainder is found in other iron-containing proteins such as myoglobin, cytochromes, and other enzymes and cofactors, or is stored as ferritin. The recommended daily intake of iron is about 8 milligrams for boys, adult men, and nonmenstruating women; 18 milligrams for menstruating women; and 27 milligrams for pregnant females. Because excess iron is toxic, the body uses several mechanisms to maintain iron homeostasis: serum protein binding, intracellular storage, and, most importantly, regulation of GI tract absorption.

The oral bioavailability of iron depends on the formulation ingested. Inorganic iron has <10% bioavailability, with ferrous iron (Fe2+) better absorbed than ferric iron (Fe3+). Common ionic formulations include ferrous chloride, ferrous fumarate, ferrous gluconate, ferrous lactate, and ferrous sulfate (Table 192-1). Nonionic formulations include carbonyl iron and iron polysaccharide (iron dextran). Most dietary iron is in the ferric form and chelated to the heme moiety. Following ingestion, the ferric ion is separated from heme and reduced to ferrous iron by a brush border ferrireductase. Chelated iron, such as that found in meat, is more readily absorbed than the iron in ionic iron preparations. There are commercially available formulations of iron ...

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