cyanocobalamin: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
cyanocobalamin: clinical details
Prescribing considerations
- Establish the cause of deficiency and avoid treatment that could obscure the diagnosis.
- Oral absorption depends substantially on intrinsic factor and may be impaired after gastrectomy or with gastrointestinal disease and malabsorption.
- For known cobalt allergy, discuss immediate or delayed sensitivity reactions and individually assess previous serious reactions.
Contraindications and cautions
- Hypersensitivity to cyanocobalamin or a formulation excipient.
- The selected lactose-containing tablet is unsuitable with galactose intolerance, total lactase deficiency or glucose-galactose malabsorption.
- The selected injection is not indicated for toxic amblyopia.
- Do not use for megaloblastic anaemia of pregnancy unless vitamin B12 deficiency is established.
Monitoring
- Assess clinical, haematological and neurological response.
- Investigate folate metabolism if megaloblastic anaemia does not respond as expected.
- During initial correction with injection, monitor potassium because hypokalaemia-associated arrhythmias have been reported.
- Monitor platelets early in treatment of megaloblastic anaemia because reactive thrombocytosis can occur.
Clinical pharmacology
Cyanocobalamin is vitamin B12, classified as ATC B03BA01. It binds to transcobalamins, is stored mainly in the liver, undergoes enterohepatic recycling, crosses the placenta and enters breast milk. A substantial proportion of an injected amount is excreted in urine.
Formulation and product differences
- The selected tablet is oral, film-coated and lactose-containing; it should preferably be taken between meals and protected from light.
- The selected injection is a clear red intramuscular solution containing sodium chloride, acetic acid and water. It is essentially sodium-free and must be protected from light.
- Injection bypasses gastrointestinal absorption; oral absorption may be unreliable where intrinsic factor is absent or malabsorption is present.
cyanocobalamin preparations and strengths
Tablet
Route: Oral
Strengths: 50 micrograms
cyanocobalamin interactions
Some medicines affect absorption, response or laboratory testing.
Metformin and other biguanides
May reduce oral absorption; clinical response and vitamin B12 status may need review.
Antacids, H2-receptor antagonists and proton-pump inhibitors
Reduced stomach acidity may decrease absorption from tablets or food.
Chloramphenicol
May reduce the haematological response.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.