Pyridoxine

Other Name(s):

vitamin B-6, pyridoxal phosphate, pyridoxamine, pyridoxol, pyridoxyl-5-phosphate

General Description:

Pyridoxine, also known as vitamin B-6, is a water-soluble vitamin. Like the other B vitamins, pyridoxine plays an important role in energy production. B-6 was isolated in 1939. It is required for the proper functioning of more than 60 enzymes in the body, especially in the synthesis of non-essential amino acids.

Pyridoxine is essential for the synthesis of neurotransmitters such as gamma-aminobutyric acid (GABA), epinephrine, norepinephrine, dopamine and serotonin. This vitamin is necessary in the conversion of glycogen to glucose (stored energy production). As a result, deficiencies can lead to sensory changes (e.g., numbness or tingling) in the extremities (peripheral neuropathy) and seizures. This vitamin is important in the formation of red blood cells -- specifically, the incorporation of iron into hemoglobin. Therefore, a deficiency of pyridoxine can result in anemia.

Medically Valid Uses:

Pyridoxine is used to treat drug-induced or diet-related pyridoxine deficiency and metabolic problems such as B-6-dependent convulsions, B-6-responsive anemia and some inborn errors of metabolism (genetic disorders). It is used to control nausea and vomiting in pregnant women.

Unsubstantiated Claims:

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Pyridoxine can be useful in decreasing PMS and preventing water retention. It acts as a diuretic, especially in PMS, and is claimed to slow the aging process. It may also lower cholesterol levels, prevent atherosclerosis (hardening of the arteries), prevent the development of carpal tunnel syndrome and prevent migraines.

Recommended Intake:

As indicated below, pyridoxine is measured in milligrams. It is available in tablet form, ranging in strength from 25 to 100 mg, with a 100 mg time-release tablet also available. The RDA is the Recommended Dietary Allowance.

Adults (over 18 years old)

Recommended Dietary Allowances (RDAs) of vitamin B6: Males (19-50 years) 1.3 milligrams; males (51 years and older) 1.7 milligrams; females (19-50 years) 1.3 milligrams; females (51 years and older) 1.5 milligrams. Some researchers think the RDA for women 19 to 50 years old should be increased to 1.5 mg to 1.7 milligrams per day. Pregnant women, 1.9 milligrams; and lactating women, 2 milligrams.

Recommended maximum daily intake of vitamin B6: Adults, pregnant, and lactating women (over 18 years) 100 milligrams. A doctor and pharmacist should be consulted for dosing in other conditions.

Children (under 18 years old)

Recommended Dietary Allowances (RDAs) of vitamin B6: Infants (0-6 months) 0.1 milligrams; infants (7-12 months) 0.3 milligrams; children (1-3 years) 0.5 milligrams; children (4-8 years) 0.6 milligrams; children (9-13 years) 1 milligram; males (14-18 years) 1 milligram per day; females (14-18 years) 1.2 milligrams per day.

Recommended maximum daily intake of vitamin B6: Children (1-3 years) 30 milligrams; (4-8 years) 40 milligrams; children (9-13 years) 60 milligrams. Males, females, pregnant, and lactating females (14-18 years) 80 milligrams.

Note: The requirement for pyridoxine increases with increased protein in the diet.

Food source

Nutrient content per 100 grams

Brewer's yeast

3.78 mg

Rice

3.59 mg

Sunflower seeds

3.59 mg

Soybeans

2.0 mg

Lentils

1.69 mg

Salmon

0.97 mg

Tuna

0.89 mg

Bran

0.85 mg

Carrots

0.65 mg

Avocado

0.6 mg

Canning vegetables may destroy over half of the pyridoxine function as a result of the heating process. Similarly, freezing vegetables may destroy up to one-third of the B-6 activity.

Although pyridoxine is relatively stable in heat (and therefore does not need to be refrigerated), it is unstable in light (specifically in ultraviolet light). Therefore, it is best stored at room temperature in light-resistant containers and left unfrozen.

There is an increased need for pyridoxine if you have a high-protein diet, asthma, breast cancer, diabetes or sickle cell anemia. Pyridoxine supplements are given to patients taking isoniazid, cycloserine and penicillamine because these drugs interfere with the availability of the vitamin.

If you consume moderate to large amounts of alcohol, or if you are a smoker, you need additional pyridoxine.

Women who are pregnant or breast-feeding may need to take vitamin supplements, but must consult a physician before doing so.

Four common problems are associated with pyridoxine deficiency. These are seizures in infants, dermatitis, anemia (both microcytic and hypochromic) and peripheral neuropathy.

Pyridoxine deficiency can cause seizures in infants whose mothers took large doses of pyridoxine to control nausea and vomiting during pregnancy. The seizures may begin within a few hours to several months after birth. They are easily controlled with pyridoxine.

The anemia resulting from a pyridoxine deficiency produces smaller than normal red blood cells (microcytic) with less than normal amounts of hemoglobin (hypochromic). In this type of anemia, the serum levels of iron are typically normal or elevated, suggesting that iron is not being incorporated into hemoglobin in the absence of vitamin B-6.

Side Effects, Toxicity and Interactions:

Megadoses of pyridoxine can cause changes in sensation, such as numbness or tingling (sensory neuropathy). An abnormal gait (ataxia) may be a byproduct of peripheral neuropathy caused by excessive doses of pyridoxine.

Pyridoxine reduces the effectiveness of levodopa (a drug used to treat Parkinson's disease). Pyridoxine can increase the body's ability to metabolize (breakdown) the levodopa. This effect is not seen with patients taking a combination of levodopa and carbidopa.

Pyridoxine supplements are warranted for patients taking isoniazid, cycloserine and penicillamine as these drugs decrease the availability of the vitamin.

Although there are reports that high doses of pyridoxine will decrease the effectiveness of phenobarbital, primidone and phenytoin, the proof of this interaction has not been established.

Additional Information:

Click here for a list of reputable Web sites with general information on nutrition.

References:

  1. Oakley GP Jr. Eat right and take a multivitamin. N Engl J Med 1998;338(15):1060-61.

  2. Claus EP, Tyler VE Jr. Pharmacognosy. 5th ed. Philadelphia, PA: Lea & Febiger; 1965.

  3. Behrman RE, Kliegman RM, Nelson EE, Vaughan VC, eds. Nelson Textbook of Pediatrics. 14th ed. Philadelphia, PA: W.B. Saunders Co.; 1992.

  4. Braunwald E, Isselbacher KJ, Petersdorf RG, Wilson JD, Martin JB, Fauci AS, eds. Harrison's Principals of Internal Medicine. 11th ed. New York, NY: McGraw-Hill; 1987.

  5. Lide DR, Frederikse HPR, eds. Handbook of Chemistry and Physics. 75th ed. Boca Raton, FL: CRC Press, Inc.; 1994.

  6. Weast RC, Astle MJ, Beyer WH, eds. Handbook of Chemistry and Physics. 65th ed. Boca Raton, FL: CRC Press, Inc.; 1984.

  7. Fischbach F, Stead L, Andrus S, Deitch S, eds. A Manual of Laboratory & Diagnostic Tests. 5th ed. Philadelphia, PA: Lippincott-Raven Publishers; 1996.

  8. Loeb S, Cahill M, et al., eds. Diagnostic Tests (Nurse's Ready Reference). Springhouse, PA: Springhouse Corporation; 1991.

  9. Pyridoxine. Facts and Comparisons. St Louis, MO: Facts & Comparisons; 1991.

  10. Pyridoxine. The Pharmacist's Guide to Vitamins, Minerals, Herb & Other Nutrients. Austin, TX: American Botanical Council; 1997.

  11. Jamieson CP, Obeid OA, Powell-Tuck J. The thiamin, riboflavin and pyridoxine status of patients on emergency admission to hospital. Clin Nutr. 1999;18(2):87-91.

  12. Nabbout R, Soufflet C, Plouin P, Dulac O. Pyridoxine dependent epilepsy: a suggestive electroclinical pattern. Arch Dis Child Fetal Neonatal Ed. 1999;81(2):F125-F129.

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