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Vitamin B12

IN THIS ARTICLE

Are there any interactions with medications?



Chloramphenicol
Interaction Rating: Major Do not take this combination.

Vitamin B12 is important for producing new blood cells. Chloramphenicol might decrease new blood cells. Taking chloramphenicol for a long time might decrease the effects of vitamin B12 on new blood cells. But most people only take chloramphenicol for a short time, so this interaction isn't a big problem.

Dosing considerations for Vitamin B12.

The following doses have been studied in scientific research:

ADULTS:

BY MOUTH:
  • The typical general supplemental dose of vitamin B12 is 1-25 mcg per day: The recommended dietary allowances (RDAs) of vitamin B12 are: 1.8 mcg; older children and adults, 2.4 mcg; pregnant women, 2.6 mcg; and breast-feeding women, 2.8 mcg. Because 10% to 30% of older people do not absorb food-bound vitamin B12 efficiently, those over 50 years should meet the RDA by eating foods fortified with B12 or by taking a vitamin B12 supplement. Supplementation of 25-100 mcg per day has been used to maintain vitamin B12 levels in older people.
  • For vitamin B12 deficiency: Vitamin B12 doses of 300-10,000 mcg daily have been used. However, some evidence suggests that the most effective oral dose is between 647-1032 mcg daily.
  • For high blood levels of homocysteine: Vitamin B12 doses of 400-500 mcg in combination with 0.54-5 mg of folic acid and 16.5 mg of pyridoxine has been used.
  • For preventing age-related macular degeneration (AMD): A combination of 1 mg of vitamin B12, 2.5 mg of folic acid, and 50 mg of pyridoxine daily has been used for 7.3 years.
APPLIED TO THE SKIN:
  • For atopic dermatitis (eczema): A specific vitamin B12 0.07% cream (Regividerm) applied twice daily has been used.
  • For psoriasis: A specific cream (Regividerm, Regeneratio Pharma AG, Wuppertal, Germany) containing avocado oil plus vitamin B12 0.7 mg/gram applied for 12 weeks twice daily has been used.
AS AN INJECTION:
  • For vitamin B12 deficiency: The usual dose is 30 mcg as an injection into the muscle or under the skin daily for 5-10 days. For maintenance therapy, 100-200 mcg once monthly is commonly used. Both cyanocobalamin and hydroxocobalamin forms are used. The usual dose for pernicious anemia-associated vitamin B12 deficiency is 100 mcg given as an injection into the muscle or under the skin once daily for 6-7 days. Then the dose may be given every other day for 7 doses followed by every 3-4 days for around 3 weeks. Then, 100 mcg should be injected every month for life. Another dosing recommendation for injectable vitamin B12 includes 1000 mcg daily for 7-10 days followed by 1000 mcg weekly for 1 month followed by 1000 mcg monthly for life.
  • For a hereditary condition that causes vitamin B12 malabsorption (Imerslund-Grasbeck disease): Vitamin B12 in the form of hydroxocobalamin has been injected into the muscle at a dose of 1 mg daily for 10 days followed by once monthly for the remainder of the person's life.
  • For cyanide poisoning:Hydroxocobalamin (Cyanokit) has been given intravenously (by IV) for a total dose of up to 10 grams.
USED IN THE NOSE:
  • For vitamin B12 deficiency: Doses of 500 mcg of vitamin B12 have been injected into one nostril weekly.
APPLIED UNDER THE SKIN:
  • For nerve damage from shingles: As an injection under the skin, 1000 mcg of vitamin B12, with or without 100 mg of thiamine, has been given six times weekly for 4 weeks.
CHILDREN:

BY MOUTH:
  • The recommended dietary allowances (RDAs) of vitamin B12 are: Infants 0-6 months, 0.4 mcg; infants 7-12 months, 0.5 mcg; children 1-3 years, 0.9 mcg; children 4-8 years, 1.2 mcg; children 9-13 years, and 1.8 mcg; older children.
AS AN INJECTION:
  • For vitamin B12 deficiency: Injecting 0.2 mcg/kg of vitamin B12 into the muscle or under the skin once daily for 2 days, followed by a 1000 mcg injection daily for 2-7 days and another 100 mcg injection weekly for 4 weeks thereafter has been used. Additional injections of 100 mcg monthly may be needed depending on level of symptom improvement and cause of vitamin B12 deficiency.

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