Hydroxocobalamin

How it works

It is converted to the active coenzymes methylcobalamin and adenosylcobalamin, which are required for methionine synthesis and methylmalonyl-CoA metabolism, supporting DNA synthesis, normal erythropoiesis and myelin integrity.

Prescribing in practice

• In severe deficiency, starting treatment can precipitate hypokalaemia as erythropoiesis resumes, so potassium should be considered during the initial response.
• Hydroxocobalamin is preferred over cyanocobalamin in the UK because its longer retention allows less frequent maintenance injections.
• Neurological involvement requires prompt and adequate replacement, and the cause of deficiency should be established as parenteral therapy is usually lifelong in malabsorption.

Monitoring

Monitor the haematological response and, in severe cases, serum potassium during early treatment, with periodic review of ongoing maintenance need.

Counselling the patient

• Vitamin B12 is given as a course of injections and then usually maintained for life when due to absorption problems.
• Tell your clinician about any numbness, tingling or balance problems.
• Keep maintenance injection appointments to prevent the deficiency returning.

Evidence & guidelines

Hydroxocobalamin is the standard UK parenteral vitamin B12 preparation for pernicious anaemia and B12-deficiency states, reflecting its favourable retention compared with cyanocobalamin.