Updated: Jun 24, 2009
Iron poisoning is a common toxicologic emergency in young children. Contributing factors include the availability of iron tablets and their candylike appearance. Ferrous sulfate tablets (20% elemental iron) are routinely administered to postpartum women, many of whom have toddlers in the family. The potential severity of iron poisoning is based on the amount of elemental iron ingested. The amount of elemental iron ingested must be calculated based on the number of tablets ingested and the percentage of elemental iron in the salt.
Children may show signs of toxicity with ingestions of 10-20 mg/kg of elemental iron. Serious toxicity is likely with ingestions of more than 60 mg/kg. Iron exerts both local and systemic effects and is corrosive to the GI mucosa and can affect the heart, lungs, and liver. Excess free iron is a mitochondrial toxin that leads to derangements in energy metabolism. Although iron poisoning is a clinical diagnosis, serum iron levels are useful in predicting the clinical course of the patient. In treatment of iron poisoning, consider both bowel decontamination with whole bowel irrigation and chelation using intravenous administration of deferoxamine.
The absorption of iron is normally very tightly controlled by the GI system. However, in overdose, local damage to the GI mucosa allows unregulated absorption, which leads to potentially toxic serum levels.
Much of the pathophysiology of iron poisoning is a result of metabolic acidosis and its effect on multiple organ systems. Toxicity manifests as local and systemic effects. Typically, iron poisoning is described in 5 sequential phases. No consensus has been reached regarding the number of phases and the times assigned to those phases. Patients may not always demonstrate all of the phases.
Phase 1
Phase 1, initial toxicity, predominantly manifests as GI effects. This phase begins during the first 6 hours postingestion and is associated with hemorrhagic vomiting, diarrhea, and abdominal pain. This is predominantly due to direct local corrosive effects of iron on the gastric and intestinal mucosa. Early hypovolemia may result from GI bleeding, diarrhea, and third spacing due to inflammation. This can contribute to tissue hypoperfusion and metabolic acidosis.
Convulsions, shock, and coma may complicate this phase if the circulatory blood volume is sufficiently compromised. In these cases, the patient progresses directly to phase 3, possibly within several hours.
Phase 2
Phase 2 is known as the latent phase and typically occurs 4-12 hours postingestion. It is usually associated with an improvement in symptoms, especially when supportive care is provided during phase 1. During this time, iron is absorbed by various tissues, and systemic acidosis increases. Clinically, the patient may appear to improve, especially to nonmedical personnel, because the vomiting that occurs in phase 1 subsides. However, laboratory analysis demonstrates progressive metabolic acidosis and, potentially, the beginning of other end-organ dysfunction (ie, elevation of transaminase levels).
Phase 3
Phase 3 typically begins within 12-24 hours postingestion, although it may occur within a few hours following a massive ingestion. Following absorption, ferrous iron is converted to ferric iron, and an unbuffered hydrogen ion is liberated. Iron is concentrated intracellularly in mitochondria and disrupts oxidative phosphorylation, resulting in free radical formation and lipid peroxidation. This exacerbates metabolic acidosis and contributes to cell death and tissue injury at the organ level.
Phase 3 consists of marked systemic toxicity caused by this mitochondrial damage and hepatocellular injury. GI fluid losses lead to hypovolemic shock and acidosis. Cardiovascular symptoms include decreased heart rate, decreased myocardial activity, decreased cardiac output, and increased pulmonary vascular resistance. The decrease in cardiac output may be related to a decrease in myocardial contractility exacerbated by the acidosis and hypovolemia. Free radicals from the iron absorption may induce damage and play a role in the impaired cardiac function.
The systemic iron poisoning in phase 3 is associated with a positive anion gap metabolic acidosis. The following explanations for the acidosis have been proposed:
A coagulopathy is observed and may be due to 2 different mechanisms. Free iron may exhibit a direct inhibitory effect on the formation of thrombin and thrombin's effect on fibrinogen in vitro. This may result in a coagulopathy. Later, reduced levels of clotting factors may be secondary to hepatic failure.
Phase 4
Phase 4 may occur 2-3 days postingestion. Iron is absorbed by Kupffer cells and hepatocytes, exceeding the storage capacity of ferritin and causing oxidative damage. Pathologic changes include cloudy swelling, periportal hepatic necrosis, and elevated transaminase levels. This may result in hepatic failure.
Phase 5
Phase 5 occurs 2-6 weeks postingestion and is characterized by late scarring of the GI tract, which causes pyloric obstruction or hepatic cirrhosis.
In 2007, 49,440 vitamin preparation exposures (some of which contain iron) in children younger than 5 years were reported to the American Association of Poison Control Centers (AAPCC).1 In 2007, no pediatric deaths due to iron poisoning were reported. This reflects the trend that iron-related fatalities are becoming less common.
Most exposures result in minimal toxicity. However, concentrated iron supplement overdoses can result in serious sequelae and death.
Most exposures involve children younger than 6 years who have ingested pediatric multivitamin preparations. Many of the serious acute ingestions follow the pattern of ingestions in general and occur in children younger than 3 years.
Most pediatric poisonings are unintentional. Specifically, in relation to iron toxicity, children may ingest the iron administered to mothers as prenatal vitamins or as postpartum supplements. Other iron exposures include ingestion of iron-fortified children's vitamins, although these tend to be less toxic. A recent study examined the effects of iron supplements in breastfed infants.2 Parents may not immediately be aware of the ingestion or the specific amount of the iron tablets ingested.
10 tablets X 38.4 mg elemental iron per tablet = 384 mg/10 kg = 38.4 mg/kg
As stated in Pathophysiology, iron toxicity is typically described in 5 sequential phases. Universal agreement does not exist as to the number of phases or the times assigned to those phases. Patients may not always demonstrate each of the phases.
Few, if any, physical examination findings are specific to iron toxicity.
Acidosis, Metabolic
Gastroenteritis
Food poisoning
Hepatic failure
The first step in treating a case of acute iron toxicity is to provide appropriate supportive care, with particular attention paid to fluid balance and cardiovascular stabilization. Initial treatment should also address the issue of preventing further absorption of iron by the GI tract.
Deferoxamine is a specific iron chelator. In the presence of ferric iron, deferoxamine forms the complex ferrioxamine, which is excreted by the kidneys. This complex imparts a reddish, vin rosé, color to the urine. Deferoxamine does not bind iron that is present in hemoglobin, hemosiderin, or ferritin. Deferoxamine is a parenteral iron chelator. It is administered IV or IM in the management of acute iron toxicity.
Freely soluble in water. Approximately 8 mg of iron is bound by 100 mg of deferoxamine. Most effective when continuously provided to the circulation by infusion. May be administered either by IM injection or by slow IV infusion. Does not effectively chelate other trace metals of nutritional importance. Provided in vials containing 500 mg or 2 g of lyophilized sterile drug. Add 2 mL or 8 mL of sterile water for injection to each vial, bringing the concentration to 250 mg/mL. For IV use, this may be diluted in 0.9% sterile saline, 5% dextrose solution, or Ringer solution.
1000 mg may be administered IV at a rate not to exceed 15 mg/kg/h; follow with a dose of 500 mg q4h for 2 doses; administer additional IV infusion slowly over 24 h; not to exceed 6 g/24 h
Alternatively, 1000 mg IM, followed by 500 mg 4 and 8 h later; depending on response, 500 mg may be administered q4-12h IM; not to exceed 6 g/24 h; IV route preferred
IV route preferred: 15 mg/kg/h IV; not to exceed 6 g/24 h
Concurrent treatment with prochlorperazine, a phenothiazine derivative, may lead to temporary impairment of consciousness
Documented hypersensitivity; patients who do not have acute iron poisoning; severe renal disease and anuria (dose reduction after the loading dose should be considered in these circumstances)
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Acute lung injury has recently been described (these patients received deferoxamine [15 mg/kg] for >24 h), and recent recommendations include higher doses of deferoxamine during the first 24 h and subsequently decreasing the dose of deferoxamine; tachycardia, hypotension, and shock may occur in patients receiving long-term therapy and could add to the cardiovascular collapse due to iron toxicity; GI adverse effects include abdominal discomfort, nausea, vomiting, and diarrhea, which may add to the symptoms of acute iron toxicity; flushing and fever are reported
Tab for PO susp. PO iron chelation agent demonstrated to reduce liver iron concentration in adults and children who receive repeated RBC transfusions. Binds iron with high affinity in a 2:1 ratio. Approved to treat chronic iron overload due to multiple blood transfusions. Treatment initiation recommended upon evidence of chronic iron overload (ie, transfusion of about 100 mL/kg packed RBCs [about 20 U for 40-kg person] and serum ferritin level consistently >1000 µg/L).
Initial: 20 mg/kg PO qd on empty stomach 30 min ac
Maintenance: Adjust dose by 5-10 mg/kg/d increments q3-6mo according to serum ferritin level trends; not to exceed 30 mg/kg/d
Note: Dissolve tab completely in water, orange juice, or apple juice, then immediately drink susp; resuspend any remaining residue in small volume of liquid and swallow
<2 years: Not established
>2 years: Administer as in adults
Data limited; do not take with aluminum-containing antacids
Documented hypersensitivity
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Common adverse effects include diarrhea, nausea, abdominal pain, headache, pyrexia, cough, and rash; may increase serum creatinine and hepatic enzyme levels; decrease dose upon persistent elevation of serum creatinine level; may cause auditory and visual disturbances; slight decreases in serum copper and zinc levels may occur; dissolve tab completely in water, orange juice, or apple juice and drink resulting susp immediately (do not swallow tab whole, do not chew or crush); measure serum ferritin levels monthly and adjust dose q3-6mo based on serum ferritin trends
Polyethylene glycol is used to increase GI transit time, decreasing absorption. It is not absorbed and is excreted entirely through the GI tract.
Laxative with strong electrolyte and osmotic effects that has cathartic actions in GI tract.
2 L/h NG
Toddlers, preschoolers, children: 250-500 mL/h PO/NG
Adolescents: Administer as in adults
Reduces effectiveness and absorption of oral medications
Documented hypersensitivity; colitis; megacolon; bowel perforation; gastric retention; GI obstruction
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Caution in ulcerative colitis and hot loop polypectomy
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Bryant SM, Leikin JB. Iron. Critical Care Toxicology. 2005;687-693.
Desferal (deferoxamine mesylate) [package insert]. East hanover, NJ: Novartis Pharmaceuticals Corporation; 2007. [Full Text].
Eldridge DL, Holstege CP. Utilizing the laboratory in the poisoned patient. Clin Lab Med. Mar 2006;26(1):13-30, vii. [Medline].
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Fine JS. Iron poisoning. Curr Probl Pediatr. Mar 2000;30(3):71-90. [Medline].
Jacobs J, Greene H, Gendel BR. Acute iron intoxication. N Engl J Med. Nov 18 1965;273(21):1124-7. [Medline].
Madiwale T, Liebelt E. Iron: not a benign therapeutic drug. Curr Opin Pediatr. Apr 2006;18(2):174-9. [Medline].
McGuigan MA. Acute iron poisoning. Pediatr Ann. Jan 1996;25(1):33-8. [Medline].
Perrone J. Iron. Goldfrank's Toxicologic Emergencies. 2006;629-637.
Siff JE, Meldon SW, Tomassoni AJ. Usefulness of the total iron binding capacity in the evaluation and treatment of acute iron overdose. Ann Emerg Med. Jan 1999;33(1):73-6. [Medline].
Tenenbein M. Position statement: whole bowel irrigation. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists. J Toxicol Clin Toxicol. 1997;35(7):753-62. [Medline].
Tenenbein M. Whole bowel irrigation in iron poisoning. J Pediatr. Jul 1987;111(1):142-5. [Medline].
iron toxicity, iron poisoning, ferrous sulfate tablets, ferrous sulfate, ferrous gluconate, ferrous fumarate, ferrous lactate, ferrous chloride, metabolic acidosis, hemorrhagic vomiting, diarrhea, abdominal pain, hepatic failure, pyloric obstruction, hepatic cirrhosis, multivitamin ingestion, treatment, diagnosis
Jennifer S Boyle, MD, PharmD, Fellow in Toxicology, University of Virginia Health System
Disclosure: Nothing to disclose.
David T Lawrence, DO, Assistant Professor, Department of Emergency Medicine, Division of Medical Toxicology, University of Virginia School of Medicine
David T Lawrence, DO is a member of the following medical societies: American College of Emergency Physicians and American College of Medical Toxicology
Disclosure: Nothing to disclose.
Christopher P Holstege, MD, Associate Professor of Emergency Medicine and Pediatrics, University of Virginia; Director, Division of Medical Toxicology, Center of Clinical Toxicology; Medical Director, Blue Ridge Poison Ctr, Associate Medical Toxicology Fellowship Director, VA Dept of Health
Christopher P Holstege, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, American Association for the Advancement of Science, American College of Emergency Physicians, American College of Medical Toxicology, American Medical Association, Medical Society of Virginia, Society for Academic Emergency Medicine, Society of Toxicology, and Wilderness Medical Society
Disclosure: Nothing to disclose.
Kathryn Clark Emery, MD, Associate Professor, Department of Pediatrics, University of Colorado Health Sciences Center; Consulting Staff, Department of Emergency Medicine, Children's Hospital of Denver
Kathryn Clark Emery, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.
Halim Hennes, MD, MS, Pediatric Emergency Medicine Research Director, Professor, Departments of Pediatrics and Emergency Medicine, Medical College of Wisconsin
Halim Hennes, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner
Jeffrey R Tucker, MD, Assistant Professor, Department of Pediatrics, Division of Emergency Medicine, University of Connecticut and Connecticut Children's Medical Center
Jeffrey R Tucker, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Pediatrics, and Massachusetts Medical Society
Disclosure: Merck Salary Employment
Paul D Petry, DO, FACOP, FAAP, Consulting Staff, Freeman Pediatric Care, Freeman Health System
Paul D Petry, DO, FACOP, FAAP is a member of the following medical societies: American Academy of Osteopathy, American Academy of Pediatrics, American College of Osteopathic Pediatricians, and American Osteopathic Association
Disclosure: Nothing to disclose.
Timothy E Corden, MD, Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin
Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, and Wisconsin Medical Society
Disclosure: Nothing to disclose.
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