Iron: Dosage Range. Toxicity. Adverse Reactions

• Therapeutic dose: 2-5 mg/kg/day; however, in many cases the equivalent of this dose may be given weekly.

• In cases of deficiency, initial effects on haemoglobin and erythrocyte concentrations take about 2 weeks but it may take 6-12 months to build iron stores.

• The Iron Status Advisory Panel advocates dietary intervention as the first treatment option for mild iron deficiency (serum ferritin 10-15 /jg/L). Trials have shown a significant increase in serum ferritin levels (26%) using dietary intervention alone.

Recommended dietary intakes — Dosage (mg/day)

Infants (0-6 months; breastfed) — 0.2

Infants (7-12 months) — 11

Children (1-13 years) — 8-9

Girls (14-18 years) — 15

Boys (14-18 years) — 11

Men (> 19 years) — 8

Women (19 to menopause) — 18

After menopause — 8

Pregnancy/lactation — 9-27

Iron is expressed as a range to allow for differences in bioavailability of iron from different foods.

Studies have shown that there can be a significant sex difference in haemoglobin and other indicators of iron status during infancy. Some of these may be genetically determined, whereas others seem to reflect an increased incidence of true iron deficiency in boys.

Toxicity

Iron toxicity causes severe organ damage and death. The most pronounced effects are haemorrhagic necrosis of the gastrointestinal tract, which manifests as vomiting, bloody diarrhea and hepatotoxicity.

Conditions that increase risk of toxicity include:

• Haemochromatosis (iron overload) — excess storage of iron in the body, which can cause organ and tissue damage (especially liver and heart) and an increased risk for hepatic carcinoma. It may be caused by an excessive oral intake, a genetic defect that causes the body to absorb more iron than normal, or repeated blood transfusions.

• Haemosiderosis — iron overload without tissue damage.

• Iron-loading anaemias — thalassaemia and sideroblastic anaemia.

Adverse Reactions

Oral supplements may cause gastrointestinal disturbances such as nausea, diarrhea, constipation, heartburn and upper gastric discomfort.

Taking supplements with food appears to reduce the possibility of gastrointestinal side-effects.

Iron toxicity and subsequent organ damage can develop from long-term excessive intake. Liquid iron preparations can discolour teeth — brush teeth after use.