What treatment is recommended for a patient with macrocytic anemia and a Vitamin B12 level of 177 pg/mL?

From the Guidelines

For a patient with a vitamin B12 level of 177 and macrocytic anemia, I recommend starting vitamin B12 replacement therapy with hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks, followed by maintenance treatment with 1 mg intramuscularly every 2–3 months for life, as suggested by the British Obesity and Metabolic Surgery Society guidelines 1, 2. The patient's macrocytic anemia is likely caused by the vitamin B12 deficiency, and treating the deficiency is essential to improve the patient's condition.

• The treatment should be initiated immediately, and the patient's complete blood count should be monitored to assess response, typically expecting reticulocytosis within 1-2 weeks and improvement in hemoglobin levels within 1-2 months.
• It's essential to identify and address the underlying cause of B12 deficiency, which may include pernicious anemia, malabsorption disorders, strict vegetarian diet, or certain medications.
• The patient should be advised to seek urgent specialist advice from a neurologist and haematologist if there is possible neurological involvement, such as unexplained sensory and/or motor and gait symptoms 2.
• Folic acid deficiency should be checked and treated only after excluding vitamin B12 deficiency, as folic acid may mask underlying vitamin B12 deficiency and precipitate subacute combined degeneration of the spinal cord 3.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Pernicious Anemia Parenteral vitamin B12 is the recommended treatment and will be required for the remainder of the patient's life. A dose of 100 mcg daily for 6 or 7 days should be administered by intramuscular or deep subcutaneous injection.

The patient has macrocytic anemia with a B12 level of 177, indicating a deficiency.

• The recommended treatment is parenteral vitamin B12.
• The initial dose is 100 mcg daily for 6 or 7 days administered by intramuscular or deep subcutaneous injection 4.

From the Research

Diagnosis and Treatment of Macrocytic Anemia

The patient's B12 level is 177, and they have macrocytic anemia. To determine the appropriate treatment, it is essential to identify the underlying cause of the macrocytic anemia.

• The most common causes of macrocytosis are alcoholism, vitamin B12 and folate deficiencies, and medications 5.
• Megaloblastic anemia is caused by deficiency or impaired utilization of vitamin B12 and/or folate, whereas nonmegaloblastic macrocytic anemia is caused by various diseases such as myelodysplastic syndrome (MDS), liver dysfunction, alcoholism, hypothyroidism, certain drugs, and less commonly inherited disorders of DNA synthesis 6.
• A peripheral smear can help differentiate between megaloblastic and nonmegaloblastic anemia. When the peripheral smear indicates megaloblastic anemia, vitamin B12 or folate deficiency is the most likely cause 5.

Treatment Options

• If the patient has a vitamin B12 deficiency, treatment with mecobalamin may be effective, as seen in a case where a patient with pernicious anemia was successfully treated with 1,500 µg mecobalamin per day 7.
• Management of macrocytic anemia is specific to the etiology identified through testing and patient evaluation 8.
• Serum vitamin B12 determination remains the best test for unmasking vitamin B12 deficiency, and it should be ordered in conjunction with serum and red cell folate determinations in the course of investigating a macrocytic anemia 9.