Ferrous Ascorbate eq to Elemental Iron 100 mg, Folic Acid 1.5 mg, Methylcobalamin 1500 mcg Tablets

Folic acid acts on megaloblastic bone marrow to produce a normoblastic marrow.

In man, an exogenous source of folate is required for nucleoprotein synthesis and the maintenance of normal erythropoiesis. Folic acid is the precursor of tetrahydrofolic acid, which is involved as a cofactor for transformylation reactions in the biosynthesis of purines and thymidylates of nucleic acids. Impairment of thymidylate synthesis in patients with folic acid deficiency is thought to account for the defective deoxyribonucleic acid (DNA) synthesis that leads to megaloblast formation and megaloblastic and macrocytic anemias.

Absorption — Folic acid is absorbed from the small intestine, primarily from the proximal portion. Folic acid appears in the plasma approximately 15 to 30 minutes after an oral dose; peak levels are generally reached within 1 hour.

Distribution — Folic acid as well as its physiologically active metabolite, L-5-methyl tetrahydro folate (L-5-MTHF), can be bound to plasma proteins when entering the systemic circulation. The fraction of folic acid bound to plasma proteins, particularly albumin, ranges between ~50% to 64%. The volume of distribution of L-5-MTHF is estimated to be 32.0 L. Tetrahydrofolic acid derivatives are distributed to all body tissues but are stored primarily in the liver. Cerebrospinal fluid levels of folic acid are several times greater than serum levels of the drug.

Metabolism — The first step in the metabolism of folic acid is its reduction to dihydrofolate via dihydrofolate reductase. Subsequently, dihydrofolate is further reduced to tetrahydrofolate (THF). THF is further converted to methylene-THF by serine-hydroxymethyltransferase and reduced to physiologically active L-5-MTHF via methylenetetrahydrofolate reductase (MTHFR).

Elimination — After intravenous administration, folic acid is rapidly cleared from the plasma. Following oral administration, majority of the dose was recovered in the urine. A majority of the metabolic products appeared in the urine after 6 hours; excretion was generally complete within 24 hours. Small amounts of orally administered folic acid have also been recovered in the feces.

Vitamin B12 supplies cofactors for methionine synthase and methylmalonyl-CoA mutase. These reactions support methionine formation and conversion of methylmalonyl-CoA to succinyl-CoA. B12 is involved in DNA synthesis, red-cell formation and nervous-system function.

Free B12 combines with intrinsic factor and is taken up in the distal ileum. Absorption becomes less efficient as the dose exceeds intrinsic-factor capacity; the NIH review reports about 2% absorption at 500 micrograms and 1.3% at 1,000 micrograms. Cyanocobalamin and hydroxocobalamin are converted into active cobalamin forms. These are oral nutrient data, not injectable-product pharmacokinetics.