FM/CFS/ME RESOURCES - Drug Database - Vitamin B-12


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Drug Database - Vitamin B-12 Vitamin B-12

Generic Name: cyanocobalamin (sye-AN-oh-koe-BAL-a-min)

Brand Names: B-12 Resin, Vitamin B-12, Vitamin B12

Classification: Vitamin

Vitamin B-12 is an essential water-soluble vitamin that is commonly found in a variety of foods such as fish, shellfish, meat, and dairy products. Vitamin B-12 is frequently used in combination with other B vitamins in a vitamin B complex formulation. It helps maintain healthy nerve cells and red blood cells and is also needed to make DNA, the genetic material in all cells. Vitamin B-12 is bound to the protein in food. Hydrochloric acid in the stomach releases B-12 from protein during digestion. Once released, B-12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream.

The human body stores several years' worth of vitamin B-12, so nutritional deficiency of this vitamin is extremely rare. Elderly are the most at risk. However, deficiency can result from being unable to use vitamin B-12. Inability to absorb vitamin B-12 from the intestinal tract can be caused by a disease known as pernicious anemia. Additionally, strict vegetarians or vegans who are not taking in proper amounts of B-12 are also prone to a deficiency state.

A day's supply of vitamin B-12 can be obtained by eating 1 chicken breast plus 1 hard-boiled egg plus 1 cup plain low-fat yogurt, or 1 cup milk plus 1 cup raisin bran.

  • Saftey Precautions
  • Side Effects & Warnings
  • Pregnancy and Breastfeeding
  • Drug Interactions
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    Saftey Precautions

    The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

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    Side Effects & Warnings

    Caution should be used in patients undergoing angioplasty since an intravenous loading dose of folic acid, vitamin B6, and vitamin B-12 followed by oral administration taken daily after coronary stenting might actually increase restenosis rates. Due to the potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents.

    Itching, rash, transitory exanthema, and urticaria have been reported. Vitamin B-12 and pyridoxine has been associated with cases of rosacea fulminans, characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to four months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy.

    Diarrhea has been reported.

    Peripheral vascular thrombosis has been reported. Treatment of vitamin B-12 deficiency can unmask polycythemia vera, which is characterized by an increase in blood volume and the number of red blood cells. The correction of megaloblastic anemia with vitamin B-12 can result in fatal hypokalemia and gout in susceptible individuals, and it can obscure folate deficiency in megaloblastic anemia. Caution is warranted.

    Vitamin B-12 is contraindicated in early Leber's disease, which is hereditary optic nerve atrophy. Vitamin B-12 can cause severe and swift optic atrophy.

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    Pregnancy and Breastfeeding

    Vitamin B-12 is likely safe when used orally in amounts that do not exceed the recommended dietary allowance (RDA).

    There is insufficient reliable information available about the safety of larger amounts of vitamin B-12 during pregnancy.

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    Drug Interactions

    Before taking Vitamin B-12, tell your doctor if you are taking any of the following medications:

    • antibiotics
    • methotrexate (Rheumatrex)
    • pyrimethamine (Daraprim)
    • colchicine
    • if you drank a lot of alcohol within the past 2 weeks

    This list is not complete and there may be other drugs that can interact with Vitamin B-12. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.

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    •, Accessed Oct. 31, 2009.

    • Retrieved Oct. 31, 2009.

    • Office of Dietary Supplements • National Institutes of Health, Dietary Supplement Fact Sheet: Vitamin B12, Retrieved Oct. 31, 2009.

    • Drugs and Supplements, Vitamin B12, Mayo Foundation for Medical Education and Research,, Retrieved Oct. 31, 2009.
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