Hydroxocobalamin

Hydroxocobalamin (Vitamin B12) is a water-soluble vitamin used for the treatment and prophylaxis of Addisonian pernicious anaemia and other macrocytic anaemias associated with vitamin B12 deficiency. It is converted into coenzyme forms essential for cell growth and replication. It is also used in Schilling test to investigate vitamin B12 absorption and deficiency states.

• Addisonian pernicious anaemia
• Other macrocytic anaemias associated with vitamin B12 deficiency
• Nutritional deficiencies
• Schilling test (vitamin B12 absorption and deficiency states)

Adult Dose (Intramuscular):

• Addisonian pernicious anaemia (without neurological involvement): Initial: 250-1,000 mcg on alternate days (1-2 weeks), then 250 mcg weekly; Maintenance: 1,000 mcg monthly
• Addisonian pernicious anaemia (with neurological complications): Initial: 1,000 mcg on alternate days; Maintenance: 1,000 mcg monthly
• Prophylaxis: 250-1,000 mcg monthly
• Nutritional deficiencies: 30 mcg daily for 5-10 days, then 100-200 mcg monthly

Child Dose (Intramuscular):

• 1-5 mg over 2 or more weeks in doses of 100 mcg, then 30-50 mcg every 4 weeks for maintenance

Schilling test: 1,000 mcg intramuscular injection

Common Side Effects:

• Allergy
• Flushing (warmth in face, ears, neck and trunk)
• Anaphylactic reaction
• Dark colored urine
• Erythema (skin redness)

Occasional: Itching exanthema, chills, fever, nausea, dizziness, anaphylactic shock (rare), acneiform and bullous eruptions (rare)

Precautions:

• Regularly monitor serum potassium levels and platelet count during therapy (to avoid hypokalemia and thrombocytosis)
• Tell doctor if pregnant, planning to become pregnant or breastfeeding
• Should not be given without first confirming the diagnosis if possible
• Regular blood examination is advisable
• If megaloblastic anaemia fails to respond, investigate folate metabolism
• Cardiac arrhythmias secondary to hypokalemia reported during initial therapy; monitor plasma potassium

Contraindications:

• Anaphylactic reaction
• Tobacco amblyopia
• Hypersensitivity to any component

Drug Interactions:

• Biguanides, para-aminosalicylic acid, potassium supplements, cholestyramine, colchicine, neomycin, ethanol, anticonvulsant drugs impair cobalamin absorption
• Anticonvulsant drugs and oral contraceptives reduce serum cobalamin levels
• Chloramphenicol may cause poor response to cyanocobalamin therapy

Food Interactions: Caution is advised when consuming alcohol with Hydroxocobalamin; consult your doctor.

Use in Pregnancy: May be unsafe; animal studies have shown harmful effects; should not be used for treatment of megaloblastic anaemia of pregnancy.

Use in Lactation: Safe during breastfeeding; does not pass into breastmilk in significant amount and is not harmful to baby.

Renal Impairment: Probably safe; dose adjustment may not be needed.

Hepatic Impairment: Probably safe; dose adjustment may not be needed.