Parenteral therapy is more expensive than oral iron preparations and is not suitable during the first trimester of pregnancy.There are cases where parenteral iron is preferable over oral iron. These are cases where oral iron is not tolerated, where the haemoglobin needs to be increased quickly (e.g. post partum, post operatively, post transfusion), where there is an underlying inflammatory condition (e.g. inflammatory bowel disease) or renal patients, the benefits of parenteral iron far outweigh the risks. In many cases, use of intravenous iron such as ferric carboxymaltose has lower risks of adverse events than a blood transfusion and as long as the person is stable is a better alternative. Ultimately this always remains a clinical decision based on local guidelines, although National Guidelines are increasingly stipulating IV iron in certain groups of patients.Soluble iron salts have a significant risk of adverse effects and can cause toxicity due to damage to cellular macromolecules. Delivering iron parenterally has utilised various different molecules to limit this. This has included dextrans, sucrose, carboxymaltose and more recently Isomaltoside 1000.One formulation of parenteral iron is iron dextran which covers the old high molecular weight (trade name DexFerrum) and the much safer low molecular iron dextrans (tradenames including Cosmofer and Infed).Iron sucrose has an occurrence of allergic reactions of less than 1 in 1000. A common side effect is taste changes, especially a metallic taste, occurring in between 1 in 10 and 1 in 100 treated patients.
Proferrin ES and Proferrin Forte) can be used when regular iron supplements such as ferrous sulfate or ferrous fumarate are not tolerated or absorbed. A clinical study demonstrated that HIP increased serum iron levels 23 times greater than ferrous fumarate on a milligram-per-milligram basis.Another alternative is ferrous glycine sulfate or ferroglycine sulfate, has less gastrointestinal side-effects than standard preparations such as iron fumarate. It is unusual among oral preparations of iron supplements in that the iron in this preparation has very high oral bioavailability, especially in the liquid formulation. This option should be evaluated before resorting to parenteral therapy. It is especially useful in iron deficiency anemia associated with autoimmune gastritis and Helicobacter pylori gastritis, where it generally has satisfactory effect.Since iron stores in the body are generally depleted, and there is a limit to what the body can process (about 2–6 mg/kg of body mass per day; i.e. for a 100 kg/220 lb man this is equal to a maximum dose of 200–600 mg/per day) without iron poisoning, this is a chronic therapy which may take 3–6 months.Due to the frequent intolerance of oral iron and the slow improvement, parenteral iron is recommended in many indications. By injection
Iron therapy (intravenously or intramuscular) is given when therapy by mouth has failed (not tolerated), oral absorption is seriously compromised (by illnesses, or when the person cannot swallow), benefit from oral therapy cannot be expected, or fast improvement is required (for example, prior to elective surgery).