What is the role of cobalamin therapy in the treatment of pernicious anemia?

Updated: Feb 18, 2019
  • Author: Srikanth Nagalla, MD, MS, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Vitamin B12 is available for therapeutic use parenterally as either cyanocobalamin or hydroxocobalamin. [20] The two forms are equally useful in the treatment of vitamin B12 deficiency, and both are nontoxic (except for rare allergic reactions). Theoretical advantages exist to using hydroxocobalamin because it is retained better in the body and is more available to cells; however, both chemical forms of cobalamin provide prompt correction.

Cobalamin is available in a solution for injection in doses ranging from 100 to 1000 µg. Most of the injected doses in excess of 50 µg are rapidly excreted in the urine. Thus, when therapy is started, repeated doses are recommended in order to replenish body stores.

A number of regimens have been recommended. One regimen begins with daily subcutaneous administration for the first week. If significant reticulocytosis confirms that therapy is successful, doses are then administered twice weekly for another 4-5 weeks. After this period, 100 µg can be administered monthly by subcutaneous or intramuscular injection. Lifetime compliance is necessary. An alternative regimen involves weekly injections of 1000 µg of vitamin B12 for 5-6 weeks, followed by monthly injections.

Cobalamin deficiency–related neurological impairment can vary in clinical presentation, including acute combined system degeneration, peripheral neuropathy, and psychosis. These neuropathies should be treated more aggressively.

Response should be monitored by reticulocyte counts, lactic dehydrogenase (LDH), and an appropriate rise in hemoglobin levels. LDH levels decrease and hemoglobin levels increase by about 1 g/dL/wk. A rise in LDH might indicate a relapse.

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