B12a; exchange of -CN for -OH group). Adverse effects, in the form of hypersensitivity reactions, are very rare. Folic Acid (B). Leafy vegetables and liver are rich in folic acid (FA). The minimal requirement is approx. 50 µg/d. Polyglutamine-FA in food is hydrolyzed to monoglutamine-FA prior to being absorbed. FA is heat labile. Causes of deficiency include: insufficient intake, malabsorption in gastrointestinal diseases, increased requirements during pregnancy. Antiepileptic drugs (phenytoin, primidone, phenobarbital) may decrease FA absorption, presumably by inhibiting the formation of monoglutamine-FA. Inhibition of dihydro-FA reductase (., by methotrexate, p. 298) depresses the formation of the active. | 138 Antianemics Drugs for the Treatment of Anemias Anemia denotes a reduction in red blood cell count hemoglobin content or both. Oxygen O2 transport capacity is decreased. Erythropoiesis A . Blood corpuscles develop from stem cells through several cell divisions. Hemoglobin is then synthesized and the cell nucleus is extruded. Erythropoiesis is stimulated by the hormone erythropoietin a glycoprotein which is released from the kidneys when renal O2 tension declines. Given an adequate production of erythropoietin a disturbance of erythropoiesis is due to two principal causes 1. Cell multiplication is inhibited because DNA synthesis is insufficient. This occurs in deficiencies of vitamin B12 or folic acid macrocytic hyperchromic anemia . 2. Hemoglobin synthesis is impaired. This situation arises in iron deficiency since Fe2 is a constituent of hemoglobin microcytic hypochromic anemia . Vitamin B12 B Vitamin B12 cyanocobalamin is produced by bacteria B12 generated in the colon however is unavailable for absorption see below . Liver meat fish and milk products are rich sources of the vitamin. The minimal requirement is about 1 pg d. Enteral absorption of vitamin B12 requires so-called intrinsic factor from parietal cells of the stomach. The complex formed with this glycoprotein undergoes endocytosis in the ileum. Bound to its transport protein transcobalamin vitamin B12 is destined for storage in the liver or uptake into tissues. A frequent cause of vitamin B12 deficiency is atrophic gastritis leading to a lack of intrinsic factor. Besides megaloblastic anemia damage to mucosal linings and degeneration of myelin sheaths with neurological sequelae will occur pernicious anemia . Optimal therapy consists in parenteral administration of cyanocobalamin or hydroxycobalamin Vitamin B12a exchange of -CN for -OH group . Adverse effects in the form of hypersensitivity reactions are very rare. Folic Acid B . Leafy vegetables and liver are rich in folic acid FA . The minimal .
