Pharmacology: Iron is an essential constituent of the body necessary for hemoglobin formation and for processes in living tissues involving oxygen. Administration of iron corrects erythropoietic abnormalities due to iron deficiency. Iron does not stimulate erythropoiesis in the absence of iron deficiency.
The vitamin B complex group functions as coenzymes for various metabolic and biochemical reactions. Thiamine is converted to thiamine pyrophosphate (TPP), a coenzyme needed for oxidation of carbohydrate. Pyridoxine hydrochloride is converted to pyridoxal phosphate, a coenzyme required in the metabolism of amino acids. Cyanocobalamin is converted to methylcobalamin and 5-deoxyadenosylcobalamin essential for carbohydrate and fat metabolism. Folic acid is required for nucleoprotein synthesis and the maintenance of normal erythropoiesis.
Pharmacokinetics: Iron is irregularly and incompletely absorbed from the gastrointestinal tract, the main sites of absorption being the duodenum and jejunum. Absorption is aided by the acid secretion of the stomach or by dietary acids and is more readily effected when the iron is in the ferrous state. Absorption is also increased in conditions of iron deficiency or in the fasting state but is decreased if the body stores are overloaded.
Ferrous iron passes through the gastrointestinal mucosa directly into the blood and is immediately bound to transferrin. Transferrin transports iron to the bone marrow where it is incorporated into hemoglobin.
Most of the iron liberated by destruction of hemoglobin is conserved and reused by the body. Iron excretion occurs primarily as desquamation of cells such as skin, GI mucosa, nails and hair; only trace amounts of iron are excreted in the bile and sweat.
The B complex vitamins are generally readily absorbed from the gastrointestinal tract. They are also widely distributed in the body tissues. Excretion is through the urine as metabolites or in the original form.