Macrocytic anemia medical therapy

In patients with deficiencies of vitamin b12 and folate causing megaloblastic anemia, medical therapy involves supplementation with cyanocobalamine and folic acid respectively based on the severity and the cause. In some cases, potassium levels can decrease (hypokalemia) in the acute phase as new cells are being generated rapidly, and this may require potassium supplementation. A reticulocytosis begins in 3-5 days and peaks in 10 days. The hematocrit will rise within 10 days. If it does not, another disorder should be suspected. Hypersegmented polymorphonuclear cells disappear in 10-14 days.

• Pharmacologic medical therapy is recommended for patients who do not improve on dietary measures.^[1][2]
• Vitamin B12 deficiency
  • Mild
    • Parenteral regimen
      • Preferred regimen (1): Cyanocobalamin 1000 μg IM q24h for 7 days, then q weekly for 4-8 weeks ^[1]
    • Oral regimen
      • Preferred regimen (1): Cyanocobalamin 500-1000 μg PO q24h^[1]
  • Severe
    • Parenteral regimen
      • Preferred regimen (1):Cyanocobalamin 1000 μg IM q24h for 7 days, then q weekly for 4-8 weeks ^[1]
    • Oral regimen
      • Preferred regimen (1): Cyanocobalamin1000-2000 μg PO q24h^[1]
  • Pernicious anemia
    • Parenteral regimen
      • Preferred regimen (1):Cyanocobalamin 1000 μg IM q24h for 7 days, then q weekly for 4-8 weeks ^[1]
      • Alternative regimen (1): Cyanocobalamin 100-1000 μg IM q24h for 1-2 weeks and then 1-3 months^[3]
    • Oral regimen
      • Preferred regimen (1): Cyanocobalamin1000-2000 μg PO q24h^[1]
  • Gastric bypass
    • Parenteral regimen
      • Preferred regimen (1):Cyanocobalamin 1000 μg IM or SQ q monthly^[4]
      • Alternative regimen (1): Cyanocobalamin 1000 μg IM q monthly^[1]
    • Oral regimen
      • Preferred regimen (1): Cyanocobalamin 350-500μg PO q24h^[4]
      • Alternative regimen (1): Cyanocobalamin 1000-2000 μg PO q24h^[1]
• Folate deficiency
  • Parenteral regimen
    • Preferred regimen (1):Folic Acid 0.4-1 mg IV q 24h and maintenance dose 0.4 mg q 24h^[5]
  • Oral regimen
    • Preferred regimen (1): Folic Acid 1-5 mg PO q 24h^[5]
    • Alternative regimen (1): Folic Acid 1-15 mg PO q 24h^[5]

Hypokalemia requiring replacement can occur in the acute phase as new cells are being generated rapidly. In some cases, potassium supplementation may be necessary.

• A reticulocytosis begins in 3-5 days and peaks in 10 days. Hematocrit will rise within 10 days. Hypersegmented neutrophils disappear in 10-14 days.
• Neurologic abnormalities may take up to 6 months to resolve if ever. The longer the disease has been present, the worse is the prognosis for recovery. Tertiary prevention measures may need to be implemented to help prevent the disability from neurologic abnormalities.

• Sulfamethoxazole/Trimethoprim (oral)
• Pyrimethamine
• Methotrexate

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