McKenna's Pharmacology for Nursing, 2e

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

Drug therapy across the lifespan

BOX 49.1

Drugs used to treat anaemias CHILDREN Proper nutrition should be established for children to provide the essential elements needed for the formation of RBCs.The cause of the anaemia should be determined to avoid prolonged problems. The safety and efficacy of epoetin alfa use have not been established for children. If the drug is used, careful dose calculation should be done based on weight and age, and the child should be monitored very closely for response, iron levels and nutrition. Iron doses for replacement therapy are determined by age. If a liquid solution is being used, the child should drink it through a straw to avoid staining of the teeth. Periodic blood counts should be performed; it may take 4 to 6 months of oral therapy to reverse an iron deficiency. Remember that iron can be toxic to children. Iron supplements should be kept out of their reach and administration monitored. Maintenance doses for folic acid have been established for children, based on age. Nutritional means should be used to establish folic acid levels whenever possible. Children with pernicious anaemia require a monthly injection of vitamin B 12 ; the nasal form has not been approved for use with children. ADULTS The underlying cause of the anaemia should be established and appropriate steps taken to reverse the cause if possible. Adults receiving epoetin alfa or darbepoetin alfa should be monitored closely for response, for the need for iron or other RBC building blocks, and for the possibility of development of pure red cell aplasia. Advertised heavily in the mass media, epoetin is often requested by adults to help restore energy. Careful teaching about the drug and how and why it is administered may be needed. Adults receiving iron replacement may experience gastrointestinal upset and frequently experience

constipation. Appropriate measures to maintain bowel function may be needed. Adults also need to know that periodic blood tests will be needed to evaluate response. Adults being treated for pernicious anaemia may opt for the nasal vitamin B 12 .These people need to receive careful instructions about the proper administration of the drug and should have nasal mucous membranes evaluated periodically. PREGNANCY AND BREASTFEEDING Proper nutrition during pregnancy and breastfeeding is often still not an adequate way to meet the increased demands of those states. Prenatal vitamins contain iron and folic acid and are usually prescribed for pregnant women. Folic acid is known to be very important for the development of the neural tube, and often women who are considering becoming pregnant are encouraged to take folic acid to build up levels for the planned pregnancy. Use of epoetin alfa or darbepoetin alfa is not recommended during pregnancy or breastfeeding because of the potential for adverse effects on the fetus or baby. Iron replacement is frequently needed postpartum to provide the iron lost during delivery.The new mother should be reminded to keep the drug out of the reach of children and not to combine prescribed iron with an over-the-counter preparation containing high levels of iron. Women maintained on vitamin B 12 before pregnancy should continue the treatment during pregnancy. Increased doses may be needed due to changes associated with the pregnancy. OLDER ADULTS Older adults may have nutritional problems related to age and may lose more iron through cellular sloughing. Older adults should be assessed for anaemia and possible causes should be evaluated. Replacement therapy in the older adult can cause the same adverse effects as are seen in the younger person. Bowel training programs may be needed to prevent severe constipation.

Myeloid tissue of bone marrow

Erythropoietin

Epoetin alfa Darbepoetin alfa Methoxy polyethylene-glycol erythropoietin beta

Haemocytoblasts

Amino acids, lipids, carbohydrates Vitamin B 12 Folic acid Iron

Macrocytic anaemia Megaloblastic anaemia Iron deficiency anaemia

Hydroxocobalamin, cyanocobalamin Folic acid, leucovorin Iron preparations

Reticulocytes

Mature erythrocytes

Circulation

120 days

Haemolysis: Liver, spleen, bone marrow

Iron Vitamin B 12

Bilirubin

FIGURE 49.2  Sites of action of drugs used to treat anaemia.

Bile