Pyridoxine

Pyridoxine[1]
IUPAC name 4,5-Bis(hydroxymethyl)-2-methylpyridin-3-ol
Identifiers
CAS number	65-23-6 Y,  58-56-0 (HCl)
PubChem	1054
SMILES CC1=NC=C(C(=C1O)CO)CO
Properties
Molecular formula	C8H11NO3
Molar mass	169.18 g mol−1
Melting point	159-162 °C
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pyridoxine is one of the compounds that can be called vitamin B₆, along with pyridoxal and pyridoxamine. It differs from pyridoxamine by the substituent at the '4' position. It is often used as 'pyridoxine hydrochloride'.

Chemistry

It is based on a pyridine ring, with hydroxyl, methyl, and hydroxymethyl substituents. It is converted to the biologically active form pyridoxal 5-phosphate.

Function in the body

Pyridoxine assists in the balancing of sodium and potassium as well as promoting red blood cell production. It is linked to cardiovascular health by decreasing the formation of homocysteine. Pyridoxine may help balance hormonal changes in women and aid the immune system. Lack of pyridoxine may cause anemia, nerve damage, seizures, skin problems, and sores in the mouth.^[2]

It is required for the production of the monoamine neurotransmitters serotonin, dopamine, norepinephrine and epinephrine, as it is the precursor to pyridoxal phosphate: cofactor for the enzyme aromatic amino acid decarboxylase. This enzyme is responsible for converting the precursors 5-hydroxytryptophan (5-HTP) into serotonin and levodopa (L-DOPA) into dopamine, noradrenaline and adrenaline. As such it has been implicated in the treatment of depression and anxiety.

Pyridoxine is not normally found in plants and plants are not the principal source of this vitamin. This vitamin is made by certain bacteria. Some vegetarians may get adequate pyridoxine simply from eating plants that have traces of soil (like potato skins). Most people get their supply of this vitamin from either milk or meat products. A very good source of pyridoxine is dragon fruit from South East Asia.^[3]

Medicinal uses

Pyroxidine is given to patients taking Isoniazid (INH) to combat the toxic side effects of the drug. It is given 10–50 mg/day to patients on to prevent peripheral neuropathy and CNS effects that are associated with the use of INH.

It is also essential for patients with extremely rare pyridoxine-dependent epilepsy, thought to be caused by mutations in the ALDH7A1 gene.

Vitamin B₆ can be compounded into a variety of different dosage forms. It can be used orally as a tablet, capsule, or solution. It can also be used as a nasal spray or for injection when in its solution form.

Vitamin B₆ is usually safe, at intakes up to 200 mg per day in adults. However, vitamin B₆ can cause neurological disorders, such as loss of sensation in legs and imbalance, when taken in high doses (200 mg or more per day - 10,000% of US RDA) over a long period of time. Vitamin B₆ toxicity can damage sensory nerves, leading to numbness in the hands and feet as well as difficulty walking. Symptoms of a pyridoxine overdose may include poor coordination, staggering, numbness, decreased sensation to touch, temperature, and vibration, and tiredness for up to several years.^[4]

A contradictory publication on pyridoxine toxicity reported that over a 6 month period or longer, 21% of women taking doses of less than 50 mg daily experienced neurological toxicity.^[5] The doses below 50 mg were not reported.

Based on the contradictory results of the two references cited above, some caution taking this vitamin at high doses and/or advise consulting with a physician or nutritional expert.

References

1. ↑ Pyridoxine at Sigma-Aldrich
2. ↑ Vitamin B1, www.HowStuffWorks.com
3. ↑ Proximate analysis of dragon fruit
4. ↑ Vitamin B6 (pyridoxine) - sources, benefits, dosage, deficiency, overdose, toxicity
5. ↑ K Dalton & MJT Dalton (1987). "Characteristics of pyridoxine overdose neuropathy syndrome". Acta Neurol Scand 76 (1): 8–11. doi:10.1111/j.1600-0404.1987.tb03536.x. PMID 3630649.