Would Vitamin B12 (Cobalamin) repletion be beneficial for a 91-year-old patient with vague dizziness and weakness, found to have a Vitamin B12 level of 220 pg/mL, and what is the recommended intramuscular injection regimen and dosing?

From the Guidelines

Vitamin B12 repletion is likely beneficial for a 91-year-old patient with vague dizziness and weakness, and a Vitamin B12 level of 220 pg/mL, and the recommended intramuscular injection regimen is hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks, followed by maintenance treatment with 1 mg intramuscularly every 2–3 months lifelong. The patient's symptoms of dizziness and weakness, although vague, may be indicative of neurological involvement, and given the patient's age, it is prudent to consider the potential benefits of Vitamin B12 repletion, as older adults often have decreased absorption and increased requirements for this vitamin 1. The recommended regimen of hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks is based on the guidelines for patients with no neurological involvement, but given the patient's symptoms, close monitoring and consideration of more frequent dosing may be necessary, and if there is possible neurological involvement, such as unexplained sensory and/or motor and gait symptoms, urgent specialist advice from a neurologist and haematologist should be sought 1. Key points to consider in the management of this patient include:

• The importance of not giving folic acid first, as it may mask underlying Vitamin B12 deficiency and precipitate subacute combined degeneration of the spinal cord 1
• The need for maintenance treatment with 1 mg intramuscularly every 2–3 months lifelong to prevent recurrence of deficiency 1
• The potential benefits of monitoring the patient for improvement in symptoms and considering rechecking Vitamin B12 levels after 1-3 months of therapy to ensure adequate repletion. Intramuscular administration of hydroxocobalamin is preferred, as it bypasses gastrointestinal absorption issues common in the elderly, and the use of hydroxocobalamin is recommended over cyanocobalamin due to its longer duration of action and potential for better efficacy in patients with neurological involvement 1.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Avoid using the intravenous route. Pernicious Anemia Parenteral vitamin B12 is the recommended treatment and will be required for the remainder of the patient's life. The oral form is not dependable A dose of 100 mcg daily for 6 or 7 days should be administered by intramuscular or deep subcutaneous injection. If there is clinical improvement and if a reticulocyte response is observed, the same amount may be given on alternate days for seven doses, then every 3 to 4 days for another 2 to 3 weeks. By this time hematologic values should have become normal This regimen should be followed by 100 mcg monthly for life.

For a 91-year-old patient with vague dizziness and weakness and a Vitamin B12 level of 220 pg/mL, Vitamin B12 repletion may be beneficial if the symptoms are related to the vitamin deficiency.

• The recommended intramuscular injection regimen is an initial dose of 100 mcg daily for 6 or 7 days.
• If clinical improvement is observed, the regimen can be adjusted to 100 mcg on alternate days for 7 doses, then every 3 to 4 days for 2 to 3 weeks.
• After that, a maintenance dose of 100 mcg monthly for life is recommended 2.

From the Research

Vitamin B12 Repletion for a 91-year-old Patient

• The patient's Vitamin B12 level is 220 pg/mL, which may indicate a deficiency, especially considering the patient's age and symptoms of dizziness and weakness 3, 4.
• Vitamin B12 deficiency becomes increasingly common with advancing age, and diverse recommendations exist for initial and maintenance therapy of deficiency states 3.

Recommended Intramuscular Injection Regimen and Dosing

• A recommended parenteral regimen uses 1000 micrograms cyanocobalamin: 5 or 6 biweekly injections for loading, and once-a-month for maintenance 3.
• High oral doses of B12 (1000 mcg and 2000 mcg) were as effective as intramuscular administration in achieving haematological and neurological responses 5.
• The most effective treatment for pernicious anemia, a cause of vitamin B12 deficiency, is intramuscular B12 4.

Oral vs. Intramuscular Vitamin B12 Administration

• Oral therapy with 300-1000 micrograms per day may be therapeutically equivalent to parenteral therapy 3.
• High-dose oral vitamin B12 replacement is standard practice in some countries and less costly than intramuscular injections 6.
• The oral route has been proved to be comparable to the intramuscular route for rectifying vitamin B12 deficiency 7, 5.