Iron Toxicity

The toxic quantity is elemental iron, not the total mass of the tablet or iron salt. A prenatal vitamin may contain several ingredients, so identify the elemental iron per tablet before estimating the ingestion. At first, iron directly injures the gastrointestinal mucosa. Vomiting, abdominal pain, diarrhea, hematemesis, and gastrointestinal blood loss can develop as the tablets cause corrosive mucosal damage. Fluid loss and bleeding can reduce circulating volume before the toxin has caused its full systemic effect. When the amount of free iron exceeds transferrin-binding capacity, unbound iron generates free radicals. These radicals trigger lipid peroxidation and cellular membrane injury; iron also disrupts mitochondrial energy production by uncoupling oxidative phosphorylation. The result is not merely gastrointestinal upset. Metabolic acidosis, hepatic necrosis, myocardial depression, vasodilation, and mixed cardiogenic–distributive shock can follow. This explains a distinctive danger of iron poisoning: the patient may have gastrointestinal hemorrhage and hypovolemia while simultaneously developing toxin-mediated vasodilation and cardiac dysfunction. A normal-looking blood pressure early in the presentation does not exclude serious injury.