Cyanocobalamin: Indication, Dosage, Side Effect, Precaution

Generic Medicine Info Patient Medicine Information

This information is not country-specific. Please refer to the Hong Kong prescribing information.

Generic Medicine Info

Indications and Dosage

Intramuscular
Macrocytic anaemia associated with vitamin B12 deficiency, Pernicious anaemia

Adult: In cases without neurological involvement: Initially, 250-1,000 mcg on alternate days for 1-2 weeks, then 250 mcg weekly until blood count returns to normal. Maintenance: 1,000 mcg monthly. In cases with neurological involvement: Initially, 1,000 mcg on alternate days, continued for as long as improvement occurs. Maintenance: 1,000 mcg monthly. Dosing recommendations may vary among individual products and between countries (refer to specific product guidelines).

Intramuscular
Prophylaxis of macrocytic anaemia associated with vitamin B12 deficiency

Adult: In cases resulting from gastrectomy and certain malabsorption syndromes: 250-1,000 mcg monthly. Dosing recommendations may vary among individual products and between countries (refer to specific product guidelines).

Intramuscular, Subcutaneous
Pernicious anaemia

Adult: 100 mcg daily for 6 or 7 days. If response is observed, give 100 mcg on alternate days for 7 doses, then every 3-4 days for another 2-3 weeks. Maintenance: 1,000 mcg monthly. All doses are given via IM or deep SC inj. Treatment and dosing recommendations may vary among individual products and between countries (refer to specific product guidelines).

Nasal
Vitamin B12 deficiency

Adult: As prevention of vitamin B₁₂ deficiency in patients with increased vitamin B₁₂ requirements, or as treatment of patients with dietary, drug-induced or malabsorption-related vitamin B₁₂ deficiency: Initially, 500 mcg (1 spray) in 1 nostril once weekly. Doses are given at least 1 hour before or 1 hour after ingestion of hot foods or liquids since hot foods may cause nasal secretions which may result in loss of medication. Treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).

Nasal
Pernicious anaemia

Adult: As maintenance therapy in patients without neurological involvement: Initially, 500 mcg (1 spray) in 1 nostril once weekly. Doses are given at least 1 hour before or 1 hour after ingestion of hot foods or liquids since hot foods may cause nasal secretions which may result in loss of medication. Treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).

Oral
Pernicious anaemia

Adult: In cases where parenteral administration is not possible or not advised: 300 mcg daily, then increase dose as necessary. Treatment and dosing recommendations may vary among individual products and between countries (refer to specific product guidelines).

Oral
Vitamin B12 deficiency

Adult: In cases due to dietary deficiencies: 50-150 mcg daily, then increase dose as necessary. Dosing recommendations may vary among individual products and between countries (refer to specific product guidelines).

Administration

Should be taken on an empty stomach. Take between meals.

Contraindications

Hypersensitivity to cyanocobalamin or cobalt.

Special Precautions

Patient with early Leber's disease and folate deficiency. Pregnancy and lactation.

Adverse Reactions

Significant: Thrombocytosis; polycythaemia vera; cobalt sensitivity reactions (e.g. chronic or subacute allergic contact dermatitis, erythema multiforme-like eruption) which may be immediate or delayed to 12-72 hours after exposure; severe optic atrophy (in patients with Leber's disease).
Gastrointestinal disorders: Nausea, diarrhoea; glossitis (nasal).
General disorders and administration site conditions: Fever, chills, malaise; inj site pain, induration or necrosis (IM).
Nervous system disorders: Headache, paraesthesia.
Skin and subcutaneous tissue disorders: Rarely, acneiform or bullous eruptions.
Potentially Fatal: Severe hypokalaemia and anaphylactic shock.

Pregnancy Category (US FDA)

IM/IV/Nasal/Parenteral/SC: C

Patient Counseling Information

Cyanocobalamin (a form of vitamin B₁₂) contains cobalt; let your doctor know if you have a known cobalt allergy. If you develop allergic reactions (e.g. rash, hives, skin eruption or blister, wheezing, difficulty breathing), inform your doctor immediately.

Monitoring Parameters

Obtain sensitivity history from the patient prior to administration. Monitor Hb, haematocrit, erythrocyte count, reticulocyte count, platelet count, serum K; serum folate and Fe levels before treatment initiation. Monitor vitamin B₁₂ 1 month after starting the treatment, then every 3-6 months thereafter. Assess for signs and symptoms of allergic reactions, including cobalt sensitivity-type reactions.

Drug Interactions

Reduced therapeutic effect with chloramphenicol. Decreased absorption with neomycin, biguanides, cimetidine, colestyramine, colchicine, methyldopa and para-aminosalicylic acid. Decreased serum concentration with oral contraceptives.

Food Interaction

Heavy alcohol consumption (>2 weeks) may cause vitamin B₁₂ malabsorption.

Lab Interference

Vitamin B₁₂ diagnostic blood assays may be invalidated by methotrexate, pyrimethamine and most antibiotics.

Action

Description:
Mechanism of Action: Cyanocobalamin, a water-soluble vitamin, is a synthetic form of vitamin B₁₂. It serves as a coenzyme for various metabolic functions (including carbohydrate and fat metabolism and protein synthesis) necessary for cell replication and haematopoiesis.
Pharmacokinetics:
Absorption: Bioavailability: Nasal: 6.1% (relative to IM). Time to peak plasma concentration: 30 minutes to 2 hours (IM or SC); 1.25 ± 1.9 hours (nasal).
Distribution: Primarily stored in the liver and bone marrow; stored in adrenals and kidneys. Crosses the placenta and enters breast milk. Plasma protein binding: Extensively bound to transcobalamins.
Metabolism: Converted in tissues into active coenzymes (methylcobalamin and deoxyadenosylcobalamin). Undergoes some enterohepatic recycling.
Excretion: Via urine (50-98% as unchanged drug).

Chemical Structure

Storage

Store between 15-30°C. Protect from light.

MIMS Class

Vitamins &/or Minerals

ATC Classification

B03BA01 - cyanocobalamin ; Belongs to the class of vitamin B12 (cyanocobalamin and analogues). Used in the treatment of anemia.

References

Anon. Cyanocobalamin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 08/01/2024.

Anon. Vitamin B12. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 08/01/2024.

B-12 Tablet (Nationwide Pharmaceutical LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/01/2024.

Buckingham R (ed). Vitamin B12 Substances. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/01/2024.

Cyanocobalamin 50 micrograms Film-coated Tablets (Glenmark Pharmaceuticals Europe Limited). MHRA. https://products.mhra.gov.uk. Accessed 08/01/2024.

Cyanocobalamin Injection (Hikma Pharmaceuticals USA Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/01/2024.

Cyanocobalamin Spray (Padagis Israel Pharmaceuticals Ltd). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/01/2024.

Cytamen 1,000 micrograms/mL Injection (RPH Pharmaceuticals AB). MHRA. https://products.mhra.gov.uk. Accessed 08/01/2024.

Joint Formulary Committee. Cyanocobalamin. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/01/2024.

Rexom Vitamin B-12 Tablet 50 mcg (KCK Pharmaceutical Industries Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia.  https://www.npra.gov.my. Accessed 08/01/2024.

Vitamin B12 (Hydroxocobalamin, Cyanocobalamin): Advise Patients with Known Cobalt Allergy to be Vigilant for Sensitivity Reactions. Medicines & Healthcare products Regulatory Agency. https://www.gov.uk/drug-safety-update. Accessed 08/01/2024.

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