What is Cyanocobalamin (Vitamin B12)?

From the Guidelines

Cyanocobalamin should be administered at a dose of 1 mg intramuscularly three times a week for 2 weeks, followed by maintenance treatment with 1 mg intramuscularly every 2–3 months for life, as recommended by the British Obesity and Metabolic Surgery Society guidelines 1. This approach is crucial for treating vitamin B12 deficiency, especially in individuals with absorption issues or after certain surgeries. The guidelines emphasize the importance of immediate treatment of vitamin B12 deficiency, particularly in cases with possible neurological involvement, such as unexplained sensory and/or motor and gait symptoms, and recommend seeking urgent specialist advice from a neurologist and haematologist in such cases 1. Key points to consider include:

• The typical food sources of vitamin B12 are animal products, including meat, fish, poultry, cheese, milk, eggs, and vitamin B12-fortified soy milk, as outlined in the KDOQI clinical practice guideline for nutrition in children with CKD 1.
• Vitamin B12 deficiency can lead to megaloblastic anemia, fatigue, neurological symptoms, and cognitive impairment, making supplementation essential for those who cannot maintain adequate levels through diet alone.
• Injections of cyanocobalamin are particularly effective for individuals with absorption problems, such as pernicious anemia or after gastric bypass surgery, as they ensure direct delivery of the vitamin into the bloodstream.
• It is essential to treat vitamin B12 deficiency before initiating folic acid supplementation, as folic acid may mask underlying vitamin B12 deficiency and precipitate subacute combined degeneration of the spinal cord, as noted in the British Obesity and Metabolic Surgery Society guidelines 1.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Vitamin B12 is essential to growth, cell reproduction, hematopoiesis, and nucleoprotein and myelin synthesis. Cyanocobalamin is quantitatively and rapidly absorbed from intramuscular and subcutaneous sites of injection; the plasma level of the compound reaches its peak within 1 hour after intramuscular injection Absorbed vitamin B12 is transported via specific B12 binding proteins, transcobalamin I and II to the various tissues. The liver is the main organ for vitamin B12 storage. Within 48 hours after injection of 100 or 1000 mcg of vitamin B12, 50 to 98% of the injected dose may appear in the urine. The major portion is excreted within the first eight hours Intravenous administration results in even more rapid excretion with little opportunity for liver storage. Gastrointestinal absorption of vitamin B12 depends on the presence of sufficient intrinsic factor and calcium ions. Intrinsic factor deficiency causes pernicious anemia, which may be associated with subacute combined degeneration of the spinal cord Prompt parenteral administration of vitamin B12 prevents progression of neurologic damage. The average diet supplies about 5 to 15 mcg/day of vitamin B12 in a protein-bound form that is available for absorption after normal digestion. Vitamin B12 is not present in foods of plant origin, but is abundant in foods of animal origin In people with normal absorption, deficiencies have been reported only in strict vegetarians who consume no products of animal origin (including no milk products or eggs). Vitamin B12 is bound to intrinsic factor during transit through the stomach; separation occurs in the terminal ileum in the presence of calcium, and vitamin B12 enters the mucosal cell for absorption It is then transported by the transcobalamin binding proteins. A small amount (approximately 1% of the total amount ingested) is absorbed by simple diffusion, but this mechanism is adequate only with very large doses. Oral absorption is considered too undependable to rely on in patients with pernicious anemia or other conditions resulting in malabsorption of vitamin B12 Cyanocobalamin is the most widely used form of vitamin B12, and has hematopoietic activity apparently identical to that of the antianemia factor in purified liver extract. Hydroxycobalamin is equally as effective as cyanocobalamin, and they share the cobalamin molecular structure.

The main use of Cyanocobalamin is for the treatment of vitamin B12 deficiency, which can cause pernicious anemia and neurologic damage.

• Key points about Cyanocobalamin include:
  • It is rapidly absorbed from intramuscular and subcutaneous sites of injection.
  • It is transported via specific B12 binding proteins to various tissues.
  • The liver is the main organ for vitamin B12 storage.
  • Intravenous administration results in rapid excretion with little opportunity for liver storage.
  • Gastrointestinal absorption depends on the presence of sufficient intrinsic factor and calcium ions.
  • Deficiencies have been reported in strict vegetarians who consume no products of animal origin.
  • Oral absorption is considered too undependable to rely on in patients with pernicious anemia or other conditions resulting in malabsorption of vitamin B12. 2

From the Research

Definition and Forms of Vitamin B12

• Vitamin B12, or cobalamin, is a water-soluble vitamin that can be ingested through food of animal origin such as eggs, milk, red meat, and poultry, fish, and shellfish 3.
• It has two active co-enzyme forms, methylcobalamin (MeCbl) and adenosylcobalamin (AdCbl), which have distinct metabolic fates and functions 4.

Causes and Symptoms of Vitamin B12 Deficiency

• Hypovitaminosis B12 is mainly caused by deficient dietary intake, reduced intestinal absorption, and certain drug interactions 3.
• Symptoms of megaloblastic anemia, a condition caused by vitamin B12 deficiency, include anemia, cytopenias, jaundice, and megaloblastic marrow morphology, as well as neurologic symptoms such as subacute combined degeneration of the cord, peripheral neuropathy, dementia, and psychotic depression 5, 6.

Treatment of Vitamin B12 Deficiency

• The treatment of hypovitaminosis B12 typically involves oral or intramuscular administration of hydroxocobalamin or cyanocobalamin 3.
• Studies have shown that oral supplementation with high doses of cyanocobalamin can be as effective as intramuscular injection in correcting plasma markers of vitamin B12 deficiency 4, 7.
• The optimal oral dose of cyanocobalamin for treating mild vitamin B12 deficiency is estimated to be between 647 to 1032 μg per day, which is significantly higher than the recommended dietary allowance 7.