CYNOZED

Indications

• Vitamin B12 deficiency
• Pernicious anemia
• Megaloblastic anemia due to vitamin B12 deficiency
• Neurological disorders associated with B12 deficiency
• Dietary vitamin B12 deficiency in strict vegetarians or vegans

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations.

Adults: Refer to the appropriate clinical guidelines or BNF for specific dosing recommendations.

Mechanism of action

Cyanocobalamin acts as a cofactor for several enzymes involved in the metabolism of fatty acids and amino acids. It is essential for the conversion of homocysteine to methionine, which is crucial for DNA synthesis and repair. Additionally, it facilitates the conversion of methylmalonyl-CoA to succinyl-CoA, a critical step in the breakdown of certain amino acids and fats.

Pharmacodynamics

Cyanocobalamin is absorbed in the intestine and is stored primarily in the liver. It influences the maturation of red blood cells and is vital for the synthesis of myelin, the protective sheath surrounding nerves. Its absence can lead to megaloblastic anemia, characterized by the production of large, immature red blood cells, and neurological manifestations due to demyelination.

Pharmacokinetics

Cyanocobalamin is absorbed in the ileum of the gastrointestinal tract, with absorption dependent on intrinsic factor, a protein secreted by the stomach. The bioavailability of cyanocobalamin is approximately 50% when administered intramuscularly or subcutaneously, whereas oral absorption is significantly lower and varies among individuals. It has a long half-life, allowing for once-monthly dosing in cases of deficiency. The vitamin is excreted mainly through urine, with small amounts eliminated in bile.

Contra-indications

• Hypersensitivity to cyanocobalamin or any excipients in the formulation
• Leber's disease (hereditary optic atrophy)

Adverse effects

• Mild diarrhea
• Itching or rash
• Anaphylactic reactions in hypersensitive individuals
• Headache
• Nausea
• Dizziness

Interactions

• Chloramphenicol may inhibit the effects of cyanocobalamin
• Certain anticonvulsants may alter vitamin B12 levels
• Alcohol may affect the absorption of cyanocobalamin

Precautions

• Use with caution in patients with a history of hypersensitivity
• Monitor vitamin B12 levels in patients with malabsorption syndromes
• Cyanocobalamin should be administered cautiously in patients with renal impairment

Pregnancy

Cyanocobalamin is generally considered safe during pregnancy. Adequate levels are important for fetal development.

Breast-feeding

Cyanocobalamin is excreted in breast milk, but it is considered safe for use during breastfeeding.

Storage

Store in a cool, dry place, away from direct light. Refrigeration may be required after opening.

Formulations

• Oral tablets
• Sublingual tablets
• Injectable solution