25.03.2 Treatments for Anaemia

Anaemia is a condition where there is decreased plasma haemoglobin levels resulting from either a decreased number of circulating red blood cells or a deficiency of functioning haemoglobin within the erythrocytes themselves. This impacts on the capacity of the red blood cells to transport oxygen and nutrients to target tissues. There are a number of different types of anaemias, each characterised by the condition of their red blood cells. In microcytic anaemias (iron deficiency, sideroblastic anaemia) the erythrocytes are smaller than normal ;: in normocytic anaemia (bone marrow failure, endocrine anaemia), cells are normal sized; in macrocytic anaemia (pernicious anaemia, folic acid deficiency, megaloblastic anaemia), cells are larger than normal; whilst in haemolytic anaemia (haemaglobinopathies, infections), the cells have autolysed. All of these anaemic states cause similar symptoms such as pallor, shortness of breath and fatigue.

Normal erythropoeisis requires a number of factors such as iron, vitamin B12 and folic acid, and a deficiency in any of these can cause anaemia. The main therapeutic approach to treating anaemia relies on replacing such deficiencies.

Iron deficiency is a common cause of anaemia and can result from chronic blood loss (e.g. menorrhagia (heavy blood loss during menstrual periods)), from gut abnormalities resulting in reduced iron absorption and in heavily menstruating or pregnant women. Iron deficiency syndromes can be treated with oral or parental iron salt (ferrous sulphate, ferrous gluconate, ferrous glycine sulphate) supplementation. Gastrointestinal disturbances, particularly constipation are the most common side effects of these treatments.

Vitamin B12 deficiency, either as a result of poor absorption of the vitamin itself or more commonly, failure to produce the intrinsic factor needed for vitamin B12 function, results in megaloblastic and pernicious anaemias. Treatment is by administration of various colbalamins (methylcobalamin, cyanocobalamin, hydroxocobalamin) which are chemically related forms of vitamin B12.

Folic acid is required for DNA and amino acid synthesis. Deficiency can be caused by increased folate demand during pregnancy and lactation, poor absorption caused by disease of the small intestine, alcoholism or concomitant treatment with folate inhibitor drugs such as methotrexate. Folica acid deficiencyleads to megaloblastic anaemia. Treatment is by oral folic acid administration.

Erythropoietin is a glycoprotein hormone, produced in the kidney, that regulates red blood cell proliferation and differentiation in the bone marrow. Recombinant human erythropoietin and darbepoetin, a variant with a longer half-life, are used to treat anaemias resulting from chronic kidney disease and from some chemotherapy treatments, particularly the platinum-containing anticancer drugs.

Sickle cell anaemia is a hereditary disorder in which a point mutation in one haemoglobin chains results in a valine being substituted for a glutamic acid. This haemoglobin, HbS, becomes sickle shaped when oxygenated resulting in impaired erythrocyte function. Treatment is with hydroxyurea which activates production of foetal haemoglobin, a process that occurs over many months, diluting the abnormal HbS.