Question

4. What are the metabolic and clinical consequences of using folic acid to treat macrocytic anemia caused by a vitamin B12 deficiency?

Answer 1

Macrocytic anemia is most often the result of vitamin B12 or folate deficiency, alcoholism, liver disease or primary marrow dysfunction( myelodysplasia or preleukemia).
vitamin B12 deficiency: vitamin b12 is involved in DNA synthesis, so that a deficiency results in abnormal cell growth and maturation.
folic acid works closely with vitamine b12 in making red blood cells and helps iron functions properly in the body.
when folates or folic acids are given to a patient with vitamin b12 deficiency the blood picture will improve but neurological manifestations will worsen.
Folic acid metabolism and mechanism of action

As folic acid is biochemically inactive, it is converted by dihydrofolate reductase to tetrahydrofolic acid and methyltetrahydrofolate. These folic acid congeners are transported by receptor-mediated endocytosis across cells where they are needed to maintain normal erythropoiesis, interconvert amino acids, methylate tRNA, generate and use formate, and synthesize purine and thymidylate nucleic acids. Using vitamin B12 as a cofactor, folic acid can normalize high homocysteine levels by remethylation of homocysteine to methionine via methionine synthetase.

Pharmacological management appears to be straightforward. It is based on supplementing deficits and building up body reserves. Follow-up of the latter is the key to a successful outcome in these patients. It is also important to consider the patient's dietary habits. Dietary advice should be given in the absence of an underlying medical condition preventing absorption of nutrients. In these cases, alternative strategies should be implemented to cover nutritional requirements.