Vitamin B6 is used where there is a special need for a
high dose of it for a period of time, or where a physician prescribes
long-term high dose B6. Higher than normal doses of vitamin B6 are used in
Carpal Tunnel Syndrome, depression, diabetes to avert neuropathy,
depressed immunity, chronic episodes of kidney stones, and PMS.(1)
Vitamin B6 is recognized for its importance in diverse
metabolic reactions and physiological actions important to overall well
being.(7)
Vitamin B6 must be converted to its aldehyde form and phosphorylated to
give pyridoxal-5-phoshate before it is biologically active, requiring
riboflavin, magnesium, and zinc as conversion cofactors.
Some of the central metabolic domains where appropriate
pyridoxal-5-phosphate levels are active include the following
categories:(7) gluconeogensis, niacin formation, lipid metabolism (plasma
pyridoxal-5-phosphate levels are positively correlated with plasma
HDL-cholesterol levels), red blood cell metabolism and function,
neurological system production of neurotransmitters and normal EEG
tracings, immune system interleukin-2 production and lymphocyte
proliferation, hormone modulation effecting endocrine-modulated
diseases.
Phenytoin blood levels can be reduced by Vitamin B6 and
folic acid in high doses. Vitamin B6 > 80 mg per day will reduce the
efficacy of phenytoin by 50 percent.
Theophylline significantly
depresses pyridoxal-5-phosphate levels, the active form of vitamin
B6.(1,8) Vitamin B6 supplementation significantly reduces the typical
adverse side effects of theophylline, including headache, nausea,
irritability, and sleep disorders.(1,9)
The expected benefits of increased pyridoxine intake may not be realized
if the user is also deficient in riboflavin (vitamin B2), magnesium, and
zinc. These cofactors operate in the liver conversion of B6 to its active
form, pyridoxal-5-phosphate.
Riboflavin and magnesium are required to convert
pyridoxine to its active form, pyridoxal-5-phosphate.(1)
Pyridoxine interacts with vitamin B12 to modulate plasma homocysteine
levels. Vitamin B6 may enhance the intracellular concentrations of
magnesium and zinc.(1)
Theophylline significantly depresses pyridoxal-5-phosphate levels which is
the active form of vitamin B6.(1,8) Vitamin B6 supplementation
significantly reduces the typical adverse side effects of theophylline,
including headache, nausea, irritability, and sleep disorders.(1,9)
Regularly consumed alcohol can retard B6 and B12 absorption and
utilization.(10)
If used for long term, penicillamine may deplete
the body of B6.(10) Oral contraceptive medications are associated with
depletion of B6. Vitamin B6 depletion can lead to depression. When OC's
are used a routine supplementation should be concerned. Vitamin B6 can be
lowered when having estrogen replacement therapy. Low B6 level is often
associated with bigger risk of depression.. (1,10) Other substances that
may deplete the body of B6 vitamin are: hydralazine if containing drugs,
corticosteroids in long term use, phenytoin and isoniazid.(1, 10)
Epilepsy drugs like barbiturates and phenobarbitol can lead to
seizures because it may be adversely lowered in plasma concentration by
B6.(10)
Supplementation of B6 vitamin can significantly lower the effectiveness of
L-dopa. Therefore, supplementation should only be prescribed by a
physician.(10)
Vitamin B6 can produce toxic effects when used at very
high doses for a protracted time.(1)
Using more than 2000 mg per day is a risk for neuropathy manifested as
tingling sensation in the feet, reduced muscle coordination, and nerve
degeneration.(1) Dosages of 500 mg per day have demonstrated neuro-toxic
effects when taken over many months or years.(3)
There are a few
reports of neuro-toxicity associated with long-term use at doses as low as
150 mg per day,(1,4,5,6) however, neuro-toxic effects are rarely seen in
the dose range of 2 to 250 mg per day, and usually seen only in chronic
use.(7)
Use 1 to 2 tablets per day, or as directed by a health
care professional.
A single dose of 100 mg of pyridoxine does not translate into a
significantly greater level of pyridoxal-5-phosphate, the active form,
than produced with 50 mg, indicating the liver rate of conversion is
almost maximal at 50 mg.(2)
1. Murray, Michael T., Encyclopedia of Nutritional
Supplements, Prima Publishing, Rocklin, CA, 1996 2. Zempleni, J.,
Pharmacokinetics of vitamin B6 supplements in humans, J Am Coll Nutr,
14:579-586, 1995 3. Cohen, M., and A. Bendich, Safety of pyridoxine - A
review of human and animal studies, Toxicol Letters, 34:129-139,
1986 4. Parry, G.J., D.E. Bredesen, Sensory neuropathy with low-dose
pyridoxine, Neurology, 35:1466-1468, 1985 5. Waterston, J.A., B.S.
Gilligan, Pyridoxine neuropathy, Med J. Aust, 146:640-642, 1987 6.
Dalton, K. Dalton, M.J.T., Characteristics of pyridoxine overdose
neuropathy syndrome, Acta Neurol Scand, 76:8, 1987 7. Leklem, James E.,
Vitamin B6, in Modern Nutrition in Health and Disease, eds., Maurice E.
Shils, James A. Olson, Moshe Shike, A. Catharine Ross, ninth edition,
Lippincott Williams & Wilkins, New York, 1999 8. Shimizu, T., et al,
Theophylline attenuates circulating vitamin B6 levels in children with
asthma, Pharmacol, 49:392-397, 1994 9. Bartel, P.R., et al, Vitamin B6
supplementation and theophylline-related effects in humans, Am J Clin
Nutr, 60:93-99, 1994 10. Graedon, Joe Teresa Graedon, Deadly Drug
Interactions, St Martin's Griffin, New York, 1995
These statements have not been evaluated by the Food and Drug Administration (FDA). Products are intended to support general well being and are not intended to treat, diagnose, mitigate, prevent, or cure any condition or disease. If conditions persist, please seek advice from your medical doctor.
