Megaloblastic Anemia Medication

Updated: Jul 17, 2021
  • Author: Srikanth Nagalla, MD, MS, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Medication Summary

Pharmacotherapy involves the administration of vitamin B12, folate, or both, as indicated. The goals of pharmacotherapy are to correct vitamin deficiencies, to prevent complications, and to reduce morbidity. For information on iron supplements, see Iron Deficiency Anemia.



Class Summary

Cyanocobalamin (vitamin B12) is used to correct vitamin B12 deficiency and folic acid is used to treat folic acid deficiencies. Cyanocobalamin does not naturally occur. It is an in vitro artifact that is readily converted to active forms of cobalamin in humans and mammals.

There are several forms of cyanocobalamin available for treatment of B12 deficiencies. Only intramuscular and oral cyanocobalamin are recommended. However, the effectiveness of oral cyanocobalamin in managing cobalamin-related neurological disorders has not been proven. Hence, oral cyanocobalamin is not recommended for subacute combined system degeneration and other cobalamin-related neurological disorders. [22]

Intravenous cobalamin is not recommended because (1) it does not accumulate since most of a dose is excreted in urine and (2) intravenous cobalamin can raise blood pressure. Intranasal cobalamin is not recommended because (1) absorption is inconsistent and not predictable and (2) it is expensive. [30, 31]

Cobalamin has been associated with allergic reactions. It is not clear whether the reactions are due to preservatives in intramuscular preparations or whether it is due to cobalamin in both parenteral and oral preparations. [31]

Cobalamin therapy for patients with Leber hereditary neuropathy, especially during early phases of the disorder, may cause blindness and is contraindicated. [31]

Cyanocobalamin (Calo-Mist, Ener-B, Nascobal)

Cyanocobalamin is most commonly given to patients. It is an in vitro artifact and is not an active form of the vitamin. However, it is converted to active forms.

Folic acid (Folvite)

Folic acid is an essential cofactor for enzymes used in DNA synthesis.


Electrolyte Supplements

Class Summary

Serum potassium levels can fall during therapy for severe cobalamin or folate deficiency and can lead to sudden death. Therefore, potassium supplements may be indicated.

Potassium chloride (K-Tab, Klor-Con, microK, Epiklor)

Potassium is essential for transmission of nerve impulses, contraction of cardiac muscle, maintenance of intracellular tonicity, skeletal and smooth muscles, and maintenance of normal renal function. Gradual potassium depletion occurs via renal excretion, through GI loss, or because of low intake.

Potassium depletion sufficient to cause 1 mEq/L drop in serum potassium requires a loss of about 100-200 mEq of potassium from body stores.