Describe oral and parenteral iron therapy with the monitoring of response and the management of iron overload.

Indications and Preparations

Oral Iron — Practical Points

• Dose: 100 to 200 mg of elemental iron daily for an adult; prescriptions must state elemental content, since the salts differ threefold
• Best absorbed on an empty stomach with vitamin C, but tolerance is much better with food; in practice, taking it with food and continuing is better than taking it correctly and stopping
• Separate from tea, coffee, milk, calcium, antacids, proton pump inhibitors, tetracyclines and fluoroquinolones by at least 2 hours
• Alternate-day dosing may be absorbed better than daily dosing, because each dose raises hepcidin for about 24 hours and blocks the next
• Adverse effects — nausea, epigastric pain, metallic taste, constipation, diarrhoea and black stools (harmless but they mask melaena and invalidate faecal occult blood tests). About a quarter of patients cannot tolerate a full dose

Parenteral Iron

• Indications — genuine intolerance of oral iron; malabsorption (coeliac disease, gastrectomy, bariatric surgery, inflammatory bowel disease); ongoing blood loss exceeding what oral iron can replace; chronic kidney disease on erythropoietin; and where rapid repletion is needed, as in late pregnancy or before surgery
• It does not raise haemoglobin faster than oral iron in a patient who takes and absorbs it; the advantage is complete and certain repletion of stores
• The total dose is calculated from the haemoglobin deficit and body weight, plus an allowance for stores
• Adverse effects — infusion reactions, fever, arthralgia, phlebitis, staining of the skin with intramuscular use, and hypophosphataemia with ferric carboxymaltose. Anaphylaxis is rare with modern preparations but resuscitation facilities must be available

Monitoring the Response and Iron Overload

• Reticulocytosis peaks at 5 to 10 days — the earliest objective sign of response and a useful early check
• Haemoglobin rises about 1 g/dL every 2 weeks; continue for 3 to 6 months after normalisation to replace stores, and confirm with ferritin
• Acute iron poisoning in children — corrosive gastrointestinal injury and haematemesis, a deceptive latent period, then shock, metabolic acidosis, hepatic necrosis and later pyloric stenosis. Treated with desferrioxamine, which chelates iron and produces a characteristic "vin rose" urine
• Chronic overload from repeated transfusion, as in thalassaemia major — causes cardiomyopathy, cirrhosis, diabetes and hypogonadism. Chelated with deferoxamine (parenteral, poorly tolerated), deferasirox (oral, once daily) and deferiprone (oral, cardiac-protective but causing agranulocytosis)

Applied Aspects

• Find the cause of the deficiency — in an adult man or postmenopausal woman, iron deficiency means gastrointestinal blood loss until proved otherwise, and requires endoscopy
• Consider hookworm and menorrhagia, which are the dominant causes in India, and treat them; deworming alongside iron is standard in endemic areas
• Distinguish iron deficiency from thalassaemia trait, which is common in India and also causes microcytosis; giving iron to a thalassaemia trait patient with normal stores is useless and potentially harmful
• Warn about black stools, or a frightened patient will stop the tablets or present with suspected melaena
• Keep iron tablets away from children; they resemble sweets and a small number can be lethal
• Anaemia Mukt Bharat supplies iron and folic acid supplementation to children, adolescents and pregnant women, with deworming and dietary diversification; the limiting factors are adherence and awareness rather than supply