ANTIANEMIC AGENTS

ANTIANAEMIC AGENTS are used to treat anemia; a deficiency in the oxygen-carrying capacity of the blood. This deficiency in the haemopoietic system can have several causes, and treatment depends on the cause. There may be a deficiency of factors necessary for formation of red blood cells (iron, folic acid, vitamin B12), an excessive destruction of red blood cells (haemolytic anaemia due to autoimmune disease or where red cells are defective), or depression of the bone marrow (aplastic anaemia after exposure to radiation or certain drugs, and after certain infections).

Iron supplements are often used to treat iron-deficient anemia. This might occur through severe haemorrhage, dietary deficiency or malabsorption of iron and in pregnancy. Supplements are usually salts of iron. Iron supplements may be administered orally, or sometimes by injection, in the form of ferrous fumarate, ferrous gluconate, ferrous glycine sulphate and ferrous sulphate.

Vitamin B12 (cyanocobalamin; extrinsic factor) is required in folate metabolism for DNA synthesis, and a deficiency leads to pernicious anaemia. It is used to supplement the diet after certain operations that remove the site of production of intrinsic factor, such as total gastrectomy. Deficiency causes megaloblastic haemopoiesis in which there is a marked disorder of formation of erythroblasts, and can be rectified by giving hydroxocobalamin.

Folic acid, or its various equivalents, is used to treat megaloblastic anemia due to deficiency, which may be due to poor diet, malabsorption syndrome or to the use of certain drugs (e.g. methotrexate or antiepileptics). It is given prophylactically to pregnant women, neonates and in chronic haemolytic anemia, including sickle-cell anaemia. In the treatment of deficiency, calcium folinate, folinic acid and folic acid are usually taken orally.

Erythropoietin (epoietin alpha and epoietin beta are recombinant forms) is a factor produced by the kidney that stimulates erythrocyte production and various other cells to produce haemopoietic growth factors — colony-stimulating factors (mirimostim and sargramostim are different recombinant forms) — which regulate the production of platelets, leucocytes and other blood cell types. Colony-stimulating factors (CSFs) stimulate blood cell progenitor cells to proliferate and differentiate. Granulocyte-colony-stimulating factors (G-CSF; filgrastim, lenograstim, molgramostim and regramostim are different recombinant forms) are produced by many cell types and are important in the development of all types of blood cells.