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Folic acid is available alone in tablet and injectable form, or in combination with other vitamins, in various multivitamin preparations. Leucovorin is a racemic mixture of 6S and 6R 5-formyl-H4PteGlu and is available as the calcium salt for use in treatment of accidental overdoses of DHFR inhibitors, such as methotrexate, or to decrease their toxicity in sensitive cells. The active 6S-isomer of leucovorin is also available as levoleucovorin calcium (Fusilev) and is dosed at one-half the rate of leucovorin with the same uses. L-Methylfolate (Deplin) is the 6S-isomer of 5-methyl-H4PteGlu. This is the biologically active isomer of 5-methyl-H4PteGlu, which is the main transport and storage form (as 5-methyl-H4PteGlun) of folates in the body. It is used in tablet form as a medical food for the treatment of methylenetetrahydrofolate reduc-tase [NAD(P)H] (EC 1.5.1.20) deficiency (MTHFR deficiency). Medical foods are substances that are regulated by the FDA and are administered enterally under the supervision of a physician intended for the dietary management of a disease that has distinctive nutritional needs.

Vitamin B12

Vitamin B12 specifically refers to cyanocobalamin, the form typically found in dietary supplements because of its high stability.214 However, the immediate precursor to the vitamin B12-derived coenzymes is hydroxocobalamin (vitamin B12b), which is formed in vivo from cyanocobalamin. Cobalamin is used to refer to any of the related cobalt-containing compounds that serve as coenzymes or their biologically active precursors as shown in Figure 28.45.

The discovery of vitamin B12 began with the unwitting description by Dr. Thomas Addison in 1855 of patients suffering from an anemia that was later identified as pernicious anemia.215 Following the rapid developments in vitamin discovery in the early 1900s, it was soon determined that a diet high in liver could reverse the effects of pernicious anemia as was clearly shown in 1926 by Minot and Murphy.216 However, concentration and identification of the vitamin was slow because the only known assay for vitamin B12 activity was the reversal of pernicious anemia in human patients. Almost 30 years had passed before Shorb217 reported in 1947 that liver extract was required for the growth of Lactobacillus lactis in similar proportions to that found to treat pernicious anemia. With an inexpensive, rapid assay for vitamin B12 activity, the crystalline form was isolated and reported simultaneously just 1 year later by Smith218 and Ricks et al.219 who suggested the name vitamin B12. Interestingly, the conversion to cyanocobalamin occurs during the purification process and is not the natural form of

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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