Iron

Key examples

• Ferrous fumerate
• Ferrous sulfate

 

Common indications

1. Treatment of iron-deficiency anaemia.
2. Prophylaxis of iron-deficiency anaemia in patients with risk factors such as poor diet, malabsorption, menorrhagia, gastrectomy, haemodialysis and infants with low birth weight.

 

Mechanisms of action

• Iron is essential for erythropoiesis (the formation of new red blood cells). It is required for the synthesis of the haem component of haemoglobin, which gives red blood cells the ability to carry oxygen.
• Iron is best absorbed in its ferrous state (Fe2+) in the duodenum and jejunum. Its absorption is increased by stomach acid and dietary acids such as ascorbic acid (vitamin C). 
• Once absorbed into the blood stream, iron is bound by transferrin. Transferrin transports it either to be used in the bone marrow for erythropoiesis, or to be stored as ferritin in the liver, reticuloendothelial system, bone marrow, spleen and skeletal muscle.
• The aim of iron therapy is to replenish iron stores. 

 

Important adverse effects

• The most common adverse effect of oral iron salts is gastrointestinal upset, including nausea, epigastric pain, constipation and diarrhoea. 
• Patients may notice that their bowel motions turn black on treatment. 
• Intravenous iron administration can cause injection site irritation and hypersensitivity reactions, including anaphylaxis.

 

Warnings

• Oral iron therapy may exacerbate bowel symptoms in patients with intestinal disease, including inflammatory bowel disease, diverticular disease and intestinal strictures. 
• Intravenous iron should be used with caution in people with an atopic predisposition due to the risk of anaphylactic reaction.

 

Important interactions

• Oral iron salts can reduce the absorption of other drugs including levothyroxine and bisphosphonates. 
• These medications should therefore be taken at least 2 hours before oral iron.