McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 4 9 Drugs used to treat anaemias

intramuscular (IM) administration of iron. Iron pol- ymaltose is given intravenously specifically for people who are undergoing chronic haemodialysis or who are in renal failure and not on dialysis but are receiving supplemental erythropoietin therapy. Iron is primarily absorbed from the small intestine by an active transport system. It is transported in the blood, bound to transferrin. Small amounts are lost daily in the sweat, urine, sloughing of skin and mucosal cells, and sloughing of intestinal cells, as well as in the menstrual flow of women. Most of the oral drug that is taken is lost in the faeces, but slowly some of the metal is absorbed into the intestine and transported to the bone marrow. It can take 2 to 3 weeks to see improvement and up to 6 to 10 months for a return to a stable iron level once a deficiency exists. It is used during pregnancy and breastfeeding to help the mother meet the increased demands for iron that occur at those times. Contraindications and cautions These drugs are contraindicated for people with known allergy to any of these preparations because severe hypersensitivity reactions have been associated with the parenteral form of iron . They also are contraindicated in the following conditions: haemochromatosis (excessive iron); haemolytic anaemias, which may increase serum iron levels and cause toxicity ; normal iron balance because the drug will not be absorbed and will just pass through the body ; and peptic ulcer, colitis or regional enteritis because the drug can be directly irritating to these tissues and can cause exacerbation of the diseases. Adverse effects The most common adverse effects associated with oral iron are related to direct GI irritation; these include GI upset, anorexia, nausea, vomiting, diarrhoea, dark stools and constipation. With increasing serum levels, iron can be directly toxic to the CNS, causing coma and even death. Box 49.3 discusses iron toxicity and drugs that are used to counteract this effect. Parenteral iron is associated with severe anaphylactic reactions, local irritation, staining of the tissues and phlebitis. See the Critical thinking scenario for additional information about iron preparations and toxicity . Clinically important drug–drug interactions Iron absorption decreases if iron preparations are taken with antacids, tetracyclines or cimetidine; if these drugs must be used, they should be spaced at least 2 hours apart. Anti-infective response to ciprofloxacin, norfloxacin or ofloxacin can decrease if these drugs are taken with iron because of a decrease in absorption; they should also be administered at least 2 hours apart. Increased iron levels occur if iron preparations are taken with

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to haemoglobin or trapped in reticuloendothelial cells for storage and eventual release and conversion into a usable form of iron for RBC production. Oral iron preparations are often used to help these people regain a positive iron balance; these preparations need to be supplemented with adequate dietary intake of iron. They are indicated for the treatment of iron-deficiency anaemias and may also be used as adjunctive therapy in people receiving an erythropoiesis-stimulating drug. The drug of choice depends on the prescriber’s personal preference and experience, and often on what kinds of samples are available to give the person. See Table 49.2 for usual indications. Pharmacokinetics Ferrous fumarate and ferrous sulfate are available for oral administration. Iron polymaltose is a parenteral form of iron given by the Z-track method. Individuals should be switched to the oral form if at all possible because of the pain associated with FIGURE 49.4  Use of the Z-track, or zigzag, technique for injections. A. Normal skin and tissues. B. Move the skin to one side. C. Insert the needle at a 90-degree angle and aspirate for blood. D. Withdraw the needle, and allow the displaced tissue to return to normal position, thereby keeping the solution from leaving the muscle tissue.