What is the most appropriate management for a patient with vitamin B12 deficiency and anemia?

Management of Vitamin B12 Deficiency with Anemia

Cyanocobalamin injections are the most appropriate management for this patient with vitamin B12 deficiency (B12 75 pg/mL) presenting with anemia (Hgb 10), pallor, and glossitis. 1, 2, 3

Initial Treatment Protocol

For vitamin B12 deficiency without neurological involvement, administer hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks, followed by maintenance treatment of 1 mg intramuscularly every 2-3 months for life. 1, 2, 3

However, since hydroxocobalamin is not universally available in the United States and cyanocobalamin is the only B12 preparation available domestically, the FDA-approved cyanocobalamin regimen is acceptable: 4

• Initial loading: 100 mcg daily for 6-7 days by intramuscular or deep subcutaneous injection 4
• Continuation: If clinical improvement and reticulocyte response occur, give the same amount on alternate days for seven doses, then every 3-4 days for another 2-3 weeks 4
• Maintenance: 100 mcg monthly for life 4

A more effective approach uses 1000 mcg cyanocobalamin instead of 100 mcg, as much greater amounts of vitamin are retained with the larger dose, with no disadvantage in cost or toxicity. 5 The recommended regimen is 5-6 biweekly injections of 1000 mcg for loading, then once monthly for maintenance. 5

Critical Timing Consideration

Never administer folic acid before treating vitamin B12 deficiency, as it may mask underlying B12 deficiency and precipitate subacute combined degeneration of the spinal cord. 1, 2, 4 Folic acid can produce hematologic remission while allowing irreversible neurological damage to progress. 4

Why Other Options Are Inappropriate

• Dietary modifications alone: Insufficient for established deficiency with anemia; oral supplementation cannot reliably correct severe deficiency 2, 4
• Fish oil: No role in treating vitamin B12 deficiency [@General Medicine Knowledge@]
• Folic acid: Contraindicated before B12 replacement; doses >0.1 mg/day may mask B12 deficiency while neurologic damage progresses 1, 4
• Omeprazole: Would worsen B12 absorption; proton pump inhibitors are a risk factor for B12 deficiency when used >12 months 6

Assessment for Neurological Involvement

Before initiating treatment, assess for neurological symptoms including: 1, 2

• Paresthesias or numbness
• Gait disturbances or ataxia
• Cognitive impairment or memory problems
• Loss of proprioception or vibratory sense

If neurological involvement is present, administer hydroxocobalamin (or cyanocobalamin if unavailable) 1 mg intramuscularly on alternate days until no further improvement, then transition to maintenance with 1 mg every 2 months. 1, 2

Monitoring Protocol

• First 48 hours: Monitor serum potassium closely and replace if necessary 4
• Days 5-7: Check hematocrit and reticulocyte count daily, then frequently until hematocrit normalizes 4
• 3 months: Recheck serum B12 levels 1
• 6 and 12 months: Repeat B12 levels in first year 1
• Annually thereafter: Once levels stabilize 1

Target homocysteine <10 μmol/L for optimal outcomes. 1

Special Consideration for This Patient

The ferritin level of 50 ng/mL suggests possible concurrent iron deficiency, which should also be addressed as it may limit the hematologic response to B12 therapy. 4 If reticulocytes do not increase appropriately after B12 treatment, iron and folate levels should be rechecked to identify complicating conditions. 4

Lifelong Treatment Requirement

This patient will require monthly injections of vitamin B12 for the remainder of their life. 4 Failure to continue treatment will result in return of anemia and development of incapacitating and irreversible damage to the spinal cord nerves. 4