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Pharmacology: Thiamine combines with adenosine triphosphate (ATP) to form a coenzyme, thiamine pyrophosphate (thiamine diphosphate, cocarboxylase), which is necessary for carbohydrate metabolism.
Pyridoxine is converted in erythrocytes to pyridoxal phosphate and to a lesser extent pyridoxamine phosphate, which act as coenzymes for various metabolic functions affecting protein, carbohydrate, and lipid utilization. Pyridoxine is involved in conversion of tryptophan to niacin or serotonin, breakdown of glycogen to glucose-1-phosphate, conversion of oxalate to glycine, synthesis of Gamma Aminobutyric Acid (GABA) within the CNS, and synthesis of heme. Cyanocobalamin acts as a coenzyme for various metabolic functions, including fat and carbohydrate metabolism and protein synthesis. It is necessary for growth, cell replication, hematopoiesis, and nucleoprotein and myelin synthesis, largely due to its effects on metabolism of methionine, folic acid, and malonic acid.
Pharmacokinetics: Thiamine: It is widely distributed to most body tissues and appears in breast milk. Thiamine is not stored to any appreciable extent in the body and amounts in excess of the body's requirements are excreted in the urine.
Pyridoxine: They are stored mainly in the liver and excreted in the urine. Pyridoxal crosses the placenta and appears in breast milk.
Cyanocobalamin: It is bound to specific plasma. They are stored in the liver, excreted in the bile and urine. It diffuses in the placenta and also in breast milk.
